BENIGN SOFT TISSUE TUMORS

INFANTILE (JUVENILE) HEMANGIOMA

Definition:

•

Infantile (juvenile) hemangioma is a form of capillary

hemangioma which occurs during infancy.

Epidemiology:

•

About 1 in every 200 live births.About 1/5 of cases are

multiple.

Sites of involvement:

•

Infantile hemangioma may be located on any body surface

but is most common in the region of the head and neck,

particulary the parotid, where follows distribution of

cutaneous nerves and arteries.

Clinical findings:

•

During early stage may resemble a common birthmark in

that it is a flat, red lesion that intensifies in color when infant

strains or cries.

•

With time become elevated with protruding appearance that

distinguished it from birthmarks and sometimes is called

strawberry nevus.

•

They appear within a few weeks after birth and rapidly

enlarge over a period of several months, achieving the

largest size in about 6-12 months; they regress over the

period of a few years. Regression show changes from

scarlet to dull grey-red and wrinkling of the skin.

•

It has been estimated that by age 7 years, 75-90% of cases

involuted, leaving small pigmented scar.

Histopathology:

•

Tumor forms multinodular mass fed by a single normally

occuring arteriole.

•

Histological features varies with its age.

•

Early lesions are characterized by plump endothelial cells

that line vascular spaces with small inconspicuous lumens.

•

Mitotic figures may be found.

•

Mast cells may be present.

•

As the lesion mature and blod flow through the lesion

commences, the endothelium becomes flattened and

resembles adult form of capillary hemangioma.

•

Maturation usually begins at the periphery of the tumors but

ultimately involves all zones.

•

Regression is accompanied by a progressive, diffuse

interstitial fibrosis.

Immunohistochemistry:

•

Immunophenotypic profile correlates with clinical phases of

infantile hemangioma:

•

Proliferative phase (0-12 months) tumor cell express

proliferative cell nuclear antigen (PCNA),

•

VEGF, and type IV collagenase

•

Involuting phase (1-5 years) CD31, vWF, GLUT1

CD31 and vWF may be lost when lesion is

•

fully involuted)

Prognosis:

•

Treatment of these lesions must be individualized and

depends on location and rate of growth.

•

Large, life threatening lesions arising on critical organs

(e.g. airways) are usually treated with glucocorticoids until

a clinical response is achieved.

•

It has been established that not complicated cases have

involuted, 75-90% of cases at age 7 years.

ANGIOMATOSIS

Definition:

•

Rare, benign but clinically extensive vascular lesion of soft.

tissue occuring in infants.

Epidemiology:

•

These lesions probably begin to grow during intrauterine life

when the limb buds to form, grow proportionately with the

fetus and involve large areas of extremities and trunk.

•

Can occurs in newborn and infants (when occur in the first

year of life is called diffuse neonatal angiomatosis)

Sites of involvement:

•

Involvement may be of two types: extensive vertical

involvement of multiple tissues (e.g., subcutis, muscle, and

bone) extensive involvement of tissue of the same type

(e.g., multiple muscles).

•

Frequently affects the lower extremities and buttock but may

occur throughout the body.

Clinical findings:

•

Usually symptoms of diffuse swelling, sometimes associated

with pain and discoloration.

Imaging:

•

CT scans appear as ill-defined nonhomogenous masses that

may resemble sarcoma exept for presence of dense areas

corresponding to thick-walled vessels.

•

Large presence of fat may appear as fatty tumors.

Histopathology:

•

Histologically angiomatosis may show two patterns.

•

The first and more common pattern show proliferation of

vessels of different size, composed of large venous,

cavernous, and capillary-sized vessels scattered in soft and

fat tissue.

•

The venous vessels are remarkable for their irregular, thick

walls that have occasional attenuations and herniations.

•

A rather characteristic features is the presence of small

vessels clustered around the wall of large vein.

•

The second pattern is identical to that of capillary

hemangiomas, exept that the nodule of tumor diffusely

infiltrate the surrounding soft tissue.

•

The abundance of fat within angiomatosis has given rise to

the alternative designation of "infiltrative angiolipoma".

Prognosis:

•

Nearly 90% of patients experienced recurrences, and 40%

had more than one recurrence within

•

5-year period.

LYMPHANGIOMA

Definition:

•

A benign, cavernous/cystic vascular lesion composed of

dilated lymphatic channels.

Epidemiology:

•

Lymphangiomas are common pediatric lesions, most often

present at birth or during first year of life.

•

Some cases may identified in Turners syndrome ( monosomy

chromosome X, 46 X) and may be found in abortuses.

•

Cavernous/cystic lymphangioma of head and neck represents

the most common type and is also called cystic hygroma.

Sites of involvement:

•

Cystic lymphangiomas are mostly located in the neck, axilla

and groin.

•

Cavernous type occurs additionally in the oral cavity, upper

trunk, limbs and abdominal sites including mesentery and

retroperitoneum.

Clinical features:

•

Lesions rather present as circumscribed painless swelling,

which are soft and fluctuant in palpation, and can show

displacement surrounding organs at mediastinal or abdominal

sites.

Imaging:

•

USG show cystic nature, angiography show poor

vascularization and CT scan reveals multiple, homogenous,

nonenhancing areas.

Gross:

•

Lymphangiomas vary from well-circumscrbed lesions made

up of one or more large interconnecting cysts to ill-defined,

sponge-like compressible lesion composed of microscopic

cysts.

•

The former were traditionally termed as cystic

lymphangiomas (cystic hygroma) and the latter as

cavernous hemangioma.

Histopathology:

•

Cavernous lymphangiomas are characterized by thin-walled,

dilated lymphatic vessels of different size, which are lined by

a flatened endothelium and frequently surrounded by

lymphocytic aggregates.

•

The lumina may be either empty or contain proteinaceous

fluid, lymphocytes and sometimes erythrocytes.

•

Larger vessels can be invested by a smooth muscle layer,

and long standing lesions may show fibrosis and

inflammatory changes.

•

Stromal mast cells are common and hemosiderin deposition

is frequently seen.

Immunohistochemistry:

•

Positive for lymphatic lineage markers D2-40, VEGFR 3.

Prognosis:

•

Recurrences are due to incomplete surgical removal, whereas

malignat transformation does not occur.

•

Lymphangiomas of neck/axilla may extend to mediastinum

and may compromise trachea, esophagus.

NEUROFIBROMA:

Definition:

•

Well-demarcated intraneural or diffusely infiltrative extraneural

tumor consisting of mixture of cell types, including Schwann

cells, perineural-like cells, and fibroblasts; multiple and

plexiform neurofibromas are typically associated with

neurofibromatosis type 1.

Epidemiology:

•

Neurofibromas are common and occur either as sporadic

solitary nodules unrelated to any apparent syndrome or as

solitary, multiple or numerous lesions in individuals with

neurofibromatosis type 1 (NF1 loss of 17q gene region).

•

All ages and both sexes are affected.

Sites of involvement:

•

Neurofibroma presents most commonly as a cutaneous nodule

(localized cutaneous neurofibroma) and less often as a

circumscribed mass in a peripheral nerve (localized intraneural

neurofibroma) or as a plexiform enlargement of a plexus or

major nerve trunk.

Clinical features:

•

Rarely painful, the tumors present as a mass.

•

The presence of multiple neurofibromas is the hallmark of NF1,

in which they are associated with pigmented cutaneous

macules (cafe-au-lait spots) as well as 'freckling', often axillary

in location.

Gross:

•

Cutaneous neurofibromas are either nodular to polypoid and

rather circumscribed, or are diffuse and involve skin and

subcutaneous tissue.

•

On cut surface, both are firm, glistening and grey-tan.

•

Plexiform neurofibromas consist of either multinodular tangles

("bag of warms") when tumor involves multiple trunks of a

plexus or rope-like lesions when multiple fascicles of a large,

non-branching nerve such as the sciatic are affected.

Histopathology:

•

Neurofibromas are composed of schwann cells with ovoid to

thin, curved to elongated nuclei and scant cytoplasm as well as

fibroblasts in a matrix of collagen fibers and Alcian blue-positive,

myxoid material.

•

The schwann cells are considerably smaller than those of

schwannomas.

•

Neurofibromas may show numerous atypical nuclei (atypical

neurofibroma) or significantly increased cellularity (cellular

neurofibroma).

•

Even in the latter mitotic figures are rare.

•

Stromal collagen formation varies in abundance and sometimes

looks like dense, retractile bundles resembling "shredded

carrots".

•

Growth of neurofibroma cells is intially along the course of

nerve fibers, which become enmeshed by tumor.

•

Neurofibroma arising from medium or large size nerve, often

remain confined to the nerve and encompassed by it thickening

epineurium.

•

In contrast, tumors arisisng in small nerves often spread

diffusely into the surrounding dermis and soft tissue.

•

Unlike schwannomas blood vessels in neurofibromas generally

lack hyalinization.

Prognosis:

•

Plexiform neurofibromas and neurofibromas of major nerves are

considered a precursor lesion to the majority of malignant

peripheral nerve sheath tumors.

•

Malignant transformation occurs in 5% of sizable plexiform

tumors, but is rare event in diffuse cutaneous and massive soft

tissue neurofibromas.

•

Patients with large neurofibromas are highly likely associated

with NF1 and should be investigated for other evidence of the

disorder.

NEUROTHECOMA

Definition:

•

Also known as nerve sheath myxoma, dermal nerve sheath

myxoma.

Epidemiology:

•

Usually arise in childhood and early adult life.

Sites of involvememt:

•

Situated in the dermis and subcutis and rare in deep soft

tissue.

•

Neurothecomas have predilection for upper portion of the body,

such as the head, neck, and shoulder.

Clinical findings:

•

Subcutaneous nodule.

Histopathology:

•

Neurothecoma has a distinctive compartmentalized appearance

due to fibrous bands divinding lesion into irregular lobules.

•

Each lobule consists of variable mixture of cells and myxoid

stroma, so tumor may appear myxoid or solid.

•

The cells vary from round to spindled and typically have little

atypia or mitotic activity.

•

Giant cells are occasionally present in the lobules, and rarely

neurites are identified among the tumor cells.

•

Although most of the cases are myxoid, there are some more

cellular, with marked cellular atypia, rare mitoses and

extension to adjacent soft tissue ( cellular neurothecoma),

which may be mistaken for sarcoma.

•

The most helpful clues to recognize neurothecoma with

atypical features are the superficial dermal location and the

distinctive septate architecture.

Immunohistochemistry:

•

Tumor cells positive for S100 and PGP9.5.

Prognosis:

•

Benign neural tumor cured with excision.

FIBROUS HAMARTOMA OF INFANCY

Definition:

•

Pediatric, benign, poorly circumscribed, superficial soft tissue

mass with three components: dense fibro-collagenous tissue,

loosely textured areas of immature rounded mesenchymal

cells and mature fat.

Epidemiology:

•

Accounting for 0.02% of all benign soft tissue, although is one

of the relatively more common tumors of fibrous tissue in early

childhood.

Sites of involvement:

•

Occurs most frequently in the anterior or posterior axillary fold,

followed by the upper arm and shoulder, thigh, groin, back,

and forearm.

•

Rarely arises in the hands and feet.

Clinical features:

•

The majority of fibrous hamartomas of infancy present in the

first 2 years of life and up to 25% are discovered at birth.

•

They do not occur after puberty, and there is boy

predominance.

•

Fibrous hamartoma of infancy is almost always a solitary

lesion, rapidly growing, freely movable mass in the subcutis

or dermis, occasionally attached to underlying fascia and

rarely involving skeletal muscle.

Gross:

•

Usually poorly circumscribed, grey-white tissue alternating

with yellow fat. Most lesions are less than 5 cm in diameter,

tumors rarely reach larger than 10 cm.

Histopathology:

•

characterized by three distinct components forming organoid

structures.

•

The well defined intersecting trabeculae of dense

fibrocollagenous tissue are composed of fibroblastic and

myofibroblastic spindle cells with bland, straight or wavy

nuclei separated by varying amounts of collagen.

•

Between fibrous trabeculae are islands of immature-appearing

small, rounded or stellate, primitive mesenchymal cells with

scant cytoplasm embedded in myxoid matrix containing

abundant hyaluronidase-sensitive acid mucopolysaccharides.

•

The primitive myxoid areas are frequently oriented around

small veins.

•

The mature fat component is interspersed among the other

two components.

•

The relative proportions of these components vary between

cases.

Prognosis:

•

Fibrous hamartoma of infancy is benign and usually cured by

local excision.

•

Rare recurrences are cured by reexcision.

INFANTILE DIGITAL FIBROMATOSIS (INCLUSION BODY FIBROMATOSIS)

Definition:

•

A benign proliferation of fibroblastic and myofibroblastic cells

that typically occur on the digits of young children. It is named

for the intracytoplasmic round inclusions staining red with

trichrome.

Epidemiology:

•

Rare lesion on the digits of young children.

Sites of involvement:

•

Typically, lesion develop on the dorsal aspect of digits of the

hands and feet.

•

More than one digit involvement is less common.

•

Involvement of the thumb or big toe is extremely unusual.

•

Rarely infantile digital fibromatosis may occur in extra-digital

sites such as the soft tissue of the arm or breast.

Clinical features:

•

Patients typically present in the first year of life.

•

There is no sex predilection.

•

The nodule on the digit usually measures less than 2.0 cm and

the overlying skin is typically taught and strched.

Gross:

•

The lesion have a uniform white/tan appearance.

•

They are typically ill defined.

Histopathology:

•

The nodules are composed of intradermal sheets and fascicles

of uniform spindle cells associated with varying amounts of

extracellular collagen.

•

They are non-encapsulated and ill defined with extension to

adjacent soft tissue. Individual cells have central elongated

nuclei and vaguely fibrillar cytoplasm.

•

The diagnostic feature is presence intracytoplasmic round to

spherical eosinophilic "inclusion". Inclusions are brightly red

trichrome positive and PAS negative.

•

These are present in minority of cells and are not always

uniformly distributed.

•

The lesional cells lack nuclear atypia and there are no

prominent mitoses present.

Prognosis:

•

Local recurrence occurs in about 50% of cases.

•

The main prognostic indicator is margin free primary excision.

•

Metastasis does not occur.

MYOFIBROMA/MYOFIBROMATOSIS

Definition:

•

Myofibroma (solitary) and myofibromatosis (multicentric) is

benign neoplasm composed of contractile myoid cells arranged

around thin-walled vessels.

•

Myofibroma(tosis) forms a morphological continuum with

myopericytoma and so-called infantile hemangiopericytoma.

Epidemiology:

•

May occur from newborn to elderly, however many cases are

diagnosed at birth or within the first two years of life.

•

Myofibroma(tosis) is more common in males.

•

The relative frequency of solitary versus multicentric forms in

unclear.

•

In adults, solitary lesions are more common.

Sites of involvement:

•

50% of solitary myofibromas occur in the

cutaneous/subcutaneous tissues of head and neck region,

followed by trunk, lower and upper extremities.

•

Other 50% occur in skeletal muscle or aponeuroses, with a

small number involving bone, predominantly the skull.

•

Myofibromatosis (multicentric) involves both soft tissue and

bone and frequently (10-20%) occurs in the deep soft tissue

and visceral location.

Clinical features:

•

Lesions may be of short or long standing duration.

•

Cutaneous lesions have the appearance of purplish macules,

simulating vascular neoplasm.

•

Subcutaneous lesions occur most often as painless, freely

movable masses while more deeply seated lesions may be

fixed.

•

Visceral lesions may cause symptoms referable to the organs

that are involved.

Imaging:

•

Soft tissue lesions varies, and can be well-circumscribed or

infiltrative, often with calcifications, either within or surrounding

the lesion.

•

Bony lesions characteristically occur as multiple elongated

radiolucent lesions within the metaphyseal regions, spering

the region adjacent to epiphysis.

Gross:

•

Nodules vary in size from 0.5 - 7.0 cm.

•

Lesion in cutaneous or subcutaneous tissue are better defined

than those in deep soft tissue.

•

Cut surface have a firm surface, greyish-white, light-tan to

brown.

•

Often have central yellow (necrotic) areas or cystic spaces

filled with caseous-like material or hemorrhage.

Histopathology:

•

At low power microscopic view show nodular or multinodular

proliferation with zonation.

•

Usually within periphery of the nodules, there are plump

myofibroblasts arranged in short fascicles or whorls.

•

Myofibroblasts are spindle shapedwith pale pink cytoplasm and

have elongated, tapering nuclei with vesicular chromatin pattern

and one or two nuclei.

•

There is no significant atypia or pleomorphism.

•

Within the center of the lesion, cells are less well differentiated,

they are round, polygonal or spindle cells with slightly larger

hyperchromatic nuclei.

•

These cells have scant cytoplasm, and are arranged around

thin-walled, irregulary branching, hemangipericytoma-like

vessels.

•

The hemangiopericytoma-like component can predominate.

•

Calcification, necrosis and stromal hyalinization are identified

frequently.

•

Mitotic activity is usually minimal.

Immunohistochemistry:

•

Tumor cells positive for vimentin and actin and negative for

S100.

Prognosis:

•

Some myofibromas regress spontaneously.

•

A small number (<10%) recur, but there are not specific factors

suggesting

•

Reexcision in most of the recurrent cases is curative.

•

The extent and location of the visceral lesions determines the

prognosis, with involvement of vital organs, leading to

cardiopulmonary or gastrointestinal complication, causing

death in rare cases.

•

Pulmonary involvement appears to be especially bad prognostic

factor. out 50% of cases.

•

The main prognostic indicator is margin free primary excision.

•

Metastasis does not occur.

JUVENILE HYALIN FIBROMATOSIS

Definition:

•

Benign disorder characterized by the accumulation of

extracellular "hyaline material" within skin, somatic soft tissues

and the skeleton mimicking tumor like masses, and typically

presents in infancy.

Epidemiology:

•

Juvenile hyaline fibromatosis is rare disorder.

•

No sex predilection.

•

Affected infants are often the progeny of affected parents.

•

Most of the time there is progressive increase in the number

and size of superficial and deep nodules with resulting deformity

and dysfunction.

Sites of involvement:

•

The tumor-like masses of hyaline material develop in the skin

(particulary the face and neck resulting in papules and nodules),

gums (causing gingival hyperplasia), periarticular soft tissue

(resulting in joint contractures) and bones (especially the skull,

long bones and phalanges).

Clinical features:

•

Patients present with skin papules affecting the face and neck,

in particular around the ears.

•

Perianal papules may resemble genital warts.

•

Periarticular deposit of hyaline material may cause joint

contracures, most commonly involving knees and elbows.

Imaging:

•

Imaging studies of affected bones reveal generalized

osteoporosis and discrete lytic lesions.

Histopathology:

•

Iindividual nodules obliterate normal tissue.

•

Composed of an admixture of plump fibroblastic cells associated

with extracellular uniform hyaline material (produced by

fibroblasts) that is non-fibrillar and eosinophilic in H&E stain.

•

In younger patients or new lesions the nodules are relatively

more cellular.

•

Fibroblasts have clear cytoplasm and may exhibit a vague

fascicular arrangement.

•

Nuclear atypia or necrosis is not seen..

•

Older lesions are less cellular and the fibroblasts may appear

compressed.

•

PAS is strongly positive and diastase resistant.

Prognosis:

•

The lesions are treated by surgical excision depending on their

location.

•

Local recurrences are high.

•

The prognosis depends on number, size and location of nodules

and the patient's functional impairement.

FIBROMATOSIS COLLI

Definition:

•

A benign, site-specific lesion that occurs in the distal

sternocleidomastoid muscle of infants.

•

The mass results in fusiform thickening of the muscle and

cervico-fascial assymetry due to its shortening (torticollis).

Epidemiology:

•

Uncommon, occurs in about 0.4% of live births.

•

There is no sex predilection.

•

The majority of cases are diagnosed before 6 months of age.

Sites of involvement:

•

Typically affects the lower one third of the sternocleidomastoid

muscle.

Clinical features:

•

The affected infants present with a smooth fusiform swelling of

the distal sternocleidomastoid muscle.

Imaging:

•

uniform isoechoic mass confined to muscle.

Gross:

•

Lesion appears as tan gritty mass confined to the muscle.

Histopathology:

•

Low cellularity, collagen rich-tissue that resembles scar or

conventional fibroma.

•

The lesion is composed of uniform plump fibroblastic and

myofibroblastic cells embedded in rich collagen.Infiltration and

entrapment of skeletal myocytes is evident.

Prognosis:

•

When diagnosed early is managed in non-surgical manner.

•

Treatment involves passive streching and physiotherapy.

•

70% of patients will have complete resolution of mass and

demonstrate normal cervico-fascial posture and movement with

this approach.

•

Surgical intervention, principally tenotomy, is required in 10-15%

of patients.

•

Worse prognosis is in patients diagnosed and treated when

older than 1 year.

INFANTILE FIBROMATOSIS, LIPOFIBROMATOSIS

Definition:

•

Benign fibro-fatty tumor of childhood with predilection for distal

extremities.

Clinical features:

•

Ill defined, slowly growing, painless mass in hands and feet and

rarely occurs in the thigh, trunk and head.

•

This tumor has been described exclusively in children.

•

Median age for surgery is 1 year.

•

Male:female ratio 2:1.

Gross:

•

The lesion usually is yellowish or whitish-tan, with fatty componenet, usually measuring 1-3 cm.

Histopathology:

•

Infantile fibromatosis has a wide morphologic spectrum

reflecting progressive stages in the differentiation of the

fibroblasts.

•

More common form of infantile fibromatosis is the diffuse

(mesenchymal) type. This form is usually found in infants in first

few months of life and is characterized by small, haphazardly

arranged, round or oval cells deposited in a myxoid background.

The cells are intermediate in appearance between primitive

mesenchymal cells and fibroblasts and they are intimately

associated with residual muscle fibers and lipocytes. Some

cases have extensive lipocytic elemts, and is reffered as

lipofibromatosis.

Peripherally located lymphocytic inflammation is often present.

Sometimes tumor may be highly cellular and mitotically active,

making distinction from infantile fibrosarcoma difficult.

•

Less common form of infantile fibromatosis (desmoid type) is

virtually indistinguishable from the adult form of fibromatosis

(desmoid tumor). This type usually occurs in children older than

5 years of age and behaves like adult desmoid tumor. Although

the morphology is similar to aduilt lesion, calcification and/or

ossification is a feature peculiar to pediatric cases.

Immunohistochemistry:

•

Spindle cells are often focally positive for CD34, BCL2, S100,

actins and EMA.

Prognosis:

•

Tumor has a high rate of nondestructive local recurrence, but no

metastatic potential.

NFLAMMATORY MYOFIBROBLASTIC TUMOR

Definition:

•

Inflammatory fibroblastic tumor (IMT) is a histologically

distinctive lesion composed of myofibroblastic spindle cells

accompanied by infiltrative inflammatory component of plasma

cells, lymphocytes and eosinophils.

•

It occurs primarily in soft tissue and viscera of children and

young adults.

Epidemiology:

•

IMT is primarily soft tissue and visceral tumor of children and

young adults.

•

The mean age is 10 years,and the median is 9 years.

•

There is slight female predominance.

•

Finding of human herpervirus-8 DNA sequences were reported,

although no exact etiology is known.

Sites of involvement:

•

IMT can occur throughout the body, and the most common sites

are the lung, mesentery, and omentum.

Clinical findings:

•

The site of origin determine the symptoms of IMT.

•

Pulmonary IMT may cause chest pain and dyspnoea, but may

be asymptomatic.

•

Adbominal tumors may cause gastrointestinal obstruction.

•

In up to 1/3 of the patients, a clinical syndrome occur with fever,

growth failure, malaise, weight loss, anemia, and elevated

erythrocyte sedimentation rate.

•

When the mass is exised, the syndrome disappears, and it

reapperance may be sign of recurrence.

Imaging:

•

Lobulated solid mass, which may be inhomogenous.

•

Calcifications are sometimes detectable.

Gross:

•

Circumscribed or multinodular firm, white or tan mass with a

whorled fleshy or myxoid cut surface.

•

Focal hemorrhage, necrosis, and calcification are seen in

minority of cases.

Histopathology:

•

Spindled myofibroblasts, fibroblasts and inflammatory cells form

three basic histological patterns of IMT.

•

Firts pattern show loosely arranged plump or spindled

myofibroblasts in an oedematous myxoid background with

abundant blood vessels and an infiltrate of plasma cells,

lymphocytes and eosinophils resemble granulation tissue,

nodular fasciitis, or other reactive processes.

•

Second pattern is characterized by a compact fascicular

spindle cell proliferation with variable myxoid and collagenized

regions and a distinctive inflammatory infiltrate with diffuse

inflammation, small aggregates of plasma cells or lymphoid

nodules.This may resemble a fibromatosis, fibrous

histiocytoma, or a smooth muscle neoplasm. In some

instances, the spindled myofibroblastic cells surround blood

vessels or bulge into vascular spaces, similar to infantile

fibromatosis or intravascular fasciitis. Ganglion-like

myofibroblasts with vesicular nuclei, eosinophilic nucleoli, and

abundant ampophilic cytoplasm are often seen these two

patterns.

•

Third pattern resembles a scar or desmoid type fibromatosis,

with pale-like collagen, lower cellularity, and relatively sparse

inflammation with plasma cells and eosinophils. Coarse or

psammomatous calcifications and osseous metaplasia are

occasionally seen.

Immunohistochemistry:

•

Positive for ALK (Anaplastic lymphoma kinase) and SMA

(smooth muscle actin).

Genetics:

•

IMT contain clonal cytogenetic rearrangements that activate the

ALK receptor tyrosine kinase gene in chromosome band 2p23.

Prognosis:

•

IMT has recurrence rate of approximately 25% related to

location, resectability and multinodualrity.

•

Although surgery is the principal treatment, regression and

response to corticosteroids and NSAID

CALCIFYING APONEUROTIC FIBROMA

Definition:

•

Benign tumor of the palms and soles of children with propensity

for local recurrence.

•

Foci of calcification, palisaded round cells and fibroblasts are

characteristic for this lesion.

Epidemiology:

•

CAF is very rare.

•

The age range spans 0-64 with a median age of 12 y/o.

•

A slight male predisposition.

Sites of involvement:

•

Palms, soles, wrists and ankles are typical sites of involvement.

•

CAF arises near tendons, fascia and aponeuroses.

•

Clinical features: CAF presents as a solitary, small, slowly

growing, poorly circumscribed non-tender mass.

Gross:

•

Firm, pale, infiltrative mass, usually<3cm, with grity cut surface.

Histopathology:

•

The typical lesion have two components.

•

Nodular deposits of calcification, each surrounded by a palisade

of rounded, chondrocyte-like cells, arranged in short, parallel

arrays.

•

Less cellular spindled, fibroblastic component between the

coalescent calcified nodules emanating into the surrounding soft

tissue.

•

Stroma of nodules is usually hyalinized but may have chondroid

features.

•

Osteoclastic giant cells may border the calcium.

Immunophenotype:

•

Positive for vimentin,smooth muscle actin, CD99 and S100.

•

Prognosis:

•

About 50% of cases have local recurrence, usually within 3 years

of diagnosis.

•

Local recurrence is more likely in patients <5 y/o but the

likelihood of recurrence is not predictable on the basis of

morphology, location or the completeness of the primary

excision.

•

Inflammatory agents have been noted in rare cases.

CALCIFYING FIBROUS PSEUDOTUMOR (CALCIFYING FIBROUS TUMOR)

Definition:

•

Rare benign fibrous lesion affecting children and young adults.

•

It is paucicellular, with fibroblasts, dense collagenization,

psammomatous and dystrophic calcification, and patchy

lymphoplasmacytic infiltrates.

Epidemiology:

•

Most soft tissue examples affect children and young adults without

gender predilection.

Sites of involvement:

•

Originally described in the subcutaneous and deep soft tissues

(extremity, trunk, neck and scrotum) but have been reported all

over the body.

Clinical features:

•

Soft tissue painless masses.

•

Visceral examples may produce site-specific symptoms.

Imaging:

•

Radiographs show well marginated, noncalcified tumor.

•

CT show apparent calcifications and may be thick, band-like or

punctate.

•

On MRI masses appear similar to fibromatoses, with a mottled

appearance and a signal closer to that of muscle than fat.

Gross:

•

Tumors are well marginated but unencapsulated, ranging in size

from <1 to 15 cm.

Histopathology:

•

Tumor is most of the time well circumscribed, unencapsulated,

paucicellular, hyalinized fibrosclerotic tissue with a variable

inflammatory infiltrate consisting of lymphocytes and plasma

cells.

•

Lymphoid aggregates may be present.

•

Calcifications, both psammomatous and dystrophic, are scattered

throughout.

Immunophenotype:

•

Lesional cells are positive for vimentn and factor XIIIa.

Prognosis:

•

Benign with occasional recurrence.

BENIGN FIBROUS HISTIOCYTOMA

Definition:

•

A benign neoplasm composed of mixture of fibroblastic and

histiocytic cells arranged in sheets of short fascicles and

accompanied by inflammatory cells, foam cells and siderophages,

which may develop within subcutaneous tissue, deep soft tissue

or in parenchymal organs.

•

When located in skin is also called dermatofibroma.

Epidemiology:

•

Deep BFH are rare and may be misdiagnosed with solitary fibrous

tumor.

•

More common is dermatofibroma.

•

May occur in any age, but most affect adults over 25 y/o.

Sites of involvement:

•

The lower limb and the head and neck region are the most

common sites.

•

Most cases involve subcutaneous tissue, but a few cases were

described in muscle, mesentery, trachea and kidney.

Clinical features:

•

Most cases present as cutaneous, solitary painless and slowly

enlarging mass.

•

May occur after minor trauma or insect bite.

Gross:

•

Cutaneous BFH are elevated or pedunculated lesions measuring

from a few milimeters to few centimeters.

Histopathology:

•

Cutaneous FH consist of nodular spindkle cell proliferation involving

dermis and occasionally subcutis.

•

Tumor is sharply demarcated laterally and typically interdigitates

with dermal collagen ("collagen traping").

•

Tumor cells are cytologically bland and generally spndle shaped

with elongated or plump vesicular nuclei and eosinophilic,

ill defined cytoplasm.

•

There is no nuclear pleomorphism, hyperchromasia, and mitosees

may be common but usually less than 5 per 10 HPF.

•

Stroma may show myxoid change or hyalinization and some

xanthoma like cells.

•

Deep fibrous histiocytoma usually is similar to cutaneous form,

but show more prominent storiform pattern and fewer secondary

elements like xanthoma cells.

Immunohistochemistry:

•

Positive XIIIa, negative CD34

Prognosis:

•

May recur locally if not incompletely excised.

JUVENILE XANTHOGRANULOMA

Definition:

•

Benign histiocytic subcutaneous lesion that usually occurs during

childhood.

Epidemiology:

•

JX usually develop during infancy and is charactarized by one or

more cutaneous nodules and less often by additional lesions in

deep soft tissue or organs.

•

As a rule, those that develop after the age of 2 years or in adults

are usually solitary.

Clinical findings:

•

About 50% of lesions develop on the head and neck, followed by

the trunck and extremities.

•

They measure from few milimeters to few centimeters.

•

Early lesions present as red papules, and the older lesions are

brown or yellow.

•

In the less common form of the disease, cutaneous lesions may be

accompanied by similar lesions in other sites, such as the eye,

lung, epicardium, oral cavity or testis.

Histopathology:

•

JX lesions are composed of sheets of histiocytes involving the

dermis and extending to, but not invading, the flattened epidermis.

•

Infiltrating histiocytes closely approach adnexal structures and

extends into sub cutis.

•

Deeply situated JX appear circumscribed but blend with or infiltrate

muscle at the periphery.

•

Histiocytes are well differentiated and exhibit little or no

pleomorphism with rare mitoses.

•

Early lesions may show some lipid features.

•

Older lesions the cells have a finely vacuolated or even

xanthomatous cytoplasm.

•

Giant cells, including Touton giant cells are typical for this lesion.

•

Usually additional components of inflammatory cells are present,

including lymphocytes, neutrophils, and eosinophils.

•

Long standing lesions may develop interstitial fibrosis, even

storiform pattern resembling conventional fibrous histiocytoma

seen in adults.

Imunohistochemistry:

•

Tumor cells are positive for CD68, alpha1 antitrypsin, lysozyme,

CD31 and factor XIIIa and negative for CD1a and S100.

Prognosis:

•

Skin lesion usually regress or at least stabilize with time, and even

large , deeply localized lesions pursue a favorable course.

GIANT CELL FIBROBLASTOMA

Definition:

•

Painless nodule or mass in subcutis with the predilection for the

back of the thigh, inguinal region and chest wall in children younger

than 5 years of age.

Epidemiology:

•

2/3 of the children were younger than 5 y/o when brought to

medical attention, and the median age was 3 y/o. Male

predominant (75%).

Clinical findings:

•

Painless nodule or mass in dermis or subcutis, with predilection for

the back of the thigh, inguinal region, and chest wall.

Gross:

•

Grey to yellow mucoid masses that are poorly circumscribed and

measure 1-8 cm.

Histopathology:

•

Composed of loosly arranged, wavy spindle cells with moderate

degree of nuclear pleomorphism that infiltrate the deep dermis and

subcutis and encircle adnexal structures in fasion similar to

dermatofibrosarcoma protuberans.

•

Tumors vary in cellularity from cellular resembling

dermatofibrosarcoma protuberans to those that are hypocellular

with a myxoid or hyaline stroma.

•

The characteristic feature of tumor are pseudovascular spaces lined

by giant cells.

Immunohistochemistry:

•

Positive for vimentin and some giant cells may express CD34,

negative for S 100 and vascular markers.

Prognosis:

•

May recur in 50% of cases, especially if not exised completely.

PLEXIFORM FIBROHISTIOCYTIC TUMOR

Definition:

•

Slowly growing plexiform fibrohistiocytic neoplasm of the deep

dermis, occurs almost exclusively in children and young adults.

Epidemiology:

•

Slowly growing mass of the deep dermis and subcutaneous tissue,

occurring almost exclusively in children and young adults.

Sites of involvement:

•

Most common location is the upper extremity (63%) followed by

the lower extremity (14%).

Clinical features:

•

Typical slow growing mass in deep dermis and subcutis.

Gross:

•

Relatively small (1-3 cm), ill-defined masses with a gray-white

trabecular appearance.

Histopathology:

•

Typical form shows two components: a differentiated fibroblastic

component and a round cell histiocytic component containing

multinucleated cells.

•

At low power microscopic view you can see numerous tiny cellular

nodules that occupy the dermis and subcutaneous tissue.

•

These nodules are composed of nests of histiocytic cells that often

contain multinucleated, osteoclast-like giant cells and occasionally

undergo focal hemorrhage. The cells in nodules are well

differentiated and do not express atypia or increased mitotic level.

•

The nodules are circumscribed by short fascicles of fibroblastic

cells that intersect slightly or ramify in the soft tissue, creating a

plexiform growth pattern.

•

The fascicles of fibroblastic cells may resemble fibromatosis, exept

that the cells are usually plumper and the fascicles shorter than

those of fibromatosis.

Immunohistochemistry:

•

CD68 positive in giant cells and mononuclear cells, smooth

muscle actin is positive in spindle cells.

Prognosis:

•

These tumors appear to be low-grade neoplasm with recurrence

12-40% within 1-2 years of the original diagnosis and excision.

FETAL RHABDOMYOMA

Definition:

•

Rare benign mesenchymal tumor that show immature skeletal

muscle differentiation and predilection for the head and neck in

children.

Sites of involvement:

•

More than 90% of fetal rhabdomyomas occurs in the soft tissue or

mucosal sites of the head and neck

(most common postauricular site).

Clinical features:

•

Most pateints < 1 year old (medain age 4 y/o).

•

Male to female ratio M:F 2.4:1.

•

Median size of the tumor is 3 cm.

•

Mostly present as well defined solitary superficial mass involving

soft tissue or mucosa of head and neck.

Gross:

•

Solitary, circumscribed, soft, grey-white to tan-pink mass with

glistening cut surface.

Histopathology:

•

Two closely related types can be distinguished by microscopy:

1) Myxoid classic type is composed of primitive oval or spindle-

shaped cells with indistinct cytoplasm, interspersed immature

skeletal muscle fibers reminiscent to fetal myotubes seen during

the seventh to tenth weeks of intrauterine life, in rich myxoid

stroma. The immature skeletal muscle cells have small uniform

nuclei with delicate chromatin and inconspicuous nucleoli with

bipolar or sometimes unipolar, eosinophilic cytoplasm. Cross

striations are rare and difficult to identified.

Intermediate cellular type is characterized by the presence of

numerous differentiated muscle fibers, less conspicuous or absent

spindle-shaped mesenchymal cells, and little or no myxoid

stroma. The predominant cells are strap-shaped muscle cells with

abundand eosinophilic cytoplasm, centrally located vesicular

nuclei, and frequent cross-striations reminiscent of the cells seen

in adult rhabdomyomas; many of the cells contain glycogen and

are often vacuolated. Others have prominent ganglion-like

rhabdomyoblasts with large vesicular nucleai and prominent

nucleoli. In some cases there is mild cellular pleomorphism, but

marked cellular atypia is not seen. Transitional forms of myxoid

and intermediate types are not rare and in fact age and duration

may play a role.

Immunophenotype:

•

Skeletal muscle cells positive for myoglobin, desmin and smooth

muscle antigen.

Genetics:

•

Multiple cases of fetal rhabdomyoma have been reported in

patients with nevoid basal cell carcinoma syndrome.

Prognosis:

•

Complete excision is curative.

LIPOBLASTOMA/LIPOBLASTOMATOSIS

Definition:

•

A lobulated, localized (lipoblastoma) or diffuse(lipoblastomatosis)

tumor, resembling fetal adipose tissue.

Epidemiology:

•

Both types of tumor are most commonly found in the first three

years of life.

•

May occasionally be found at birth or in older children.

•

There is male predilection.

Sites of involvement:

•

The extremities are most common location but location in

mediastinum, retroperitoneum and head and neck areas was

described.

Clinical features:

•

Most patients present with slow growing soft tissue nodule/mass,

well circumscribed and confined to the subcutis in case of

lipoblastoma , infiltrating deeper muscle in case of

lipoblastomatosis.

Gross:

•

Relatively small lesions (2-5 cm), showing fatty looking tissue with

gelatinous areas.

Histopathology:

•

Lipoblastoma shows lobulated architecture with an admixture of

mature and immature adipocytes, the latter corresponding to

lipoblasts in various stages of development.

•

Depending of age of the patient, the lipoblast may be very scarse

and lesion may be dominated by lipoma-like component

(mostly in older patients).

•

Connective tissue septa separate lobules.

•

Lobulation is less prominent in lipoblastomatosis.

•

Matrix can be quite myxoid, with a plexiform vascular pattern, thus

mimicking myxoid liposarcoma.

•

Occasionally lipoblastoma(tosis) may show extramedulary

hematopoiesis or cells resembling brown fat.

•

Cellular maturation has been described, leading to lipoma-like

picture.

Genetics:

•

Characteristic cytogenetic feature is rearrangement of 8q11-13,

which has been found in majority of cases.

Prognosis:

•

Lipoblastoma is benign and malignant transformation or

metastatsis does not occur.

•

Recurrences are described in 9-22% of cases mainly in

lipoblastomatosis.

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LIPOMATOSIS OF NERVE (FIBROLIPOMATOUS HAMARTOMA)

Definition:

•

Lipomatosis of nerve is characterized by infiltration of the

epineurium by adipose and fibrous tissue.

•

Tissue grows between and around nerve bundles causing

enlargement of involved nerve.

Epidemiology:

•

Frequently first noted at birth or in early childhood.

•

In the largest reported series patients ranged in ages 11 to 39

y/o. In some cases it is associated with macrodactyly of the

digits innervated by the affected nerve.

•

Females predominate when lipo-fibroma is accompanied by

macrodactyly, whereas males are more commonly affected

when macrodactyly is absent.

Sites of involvement:

•

Medial nerve and its digital branches are most commonly

affected followed by the ulnar nerve.

Clinical features:

•

Presents with a gradually enlarged mass in the affected area

that may be asymptomatic or associated with motor or

sensory deficits.

•

Patients with macrodactyly have symmetrical or assymetrical

enlargementf of affected finger(s) with enlargement of the

involved bones.

Imaging:

•

Fat around fascicles of enlarged nerve (usually median).

Gross:

•

Grossly there is fusiform enlargement of the nerve by yellow

fibrofatty tissue, which is generally confined within the

epineural sheath.

Histopathology:

•

The epineurial and perineurial compartments of enlarged nerve

are infiltrated by mature adipose tissue which dissects and

separate nerve bundles.

•

Concentric perineural fibrosis is additional prominent feature.

•

The affected nerve may also show other changes as perineural

septation, microfascicle formation and pseudoonion bulb

formation mimicking an intraneural perineurioma.

Prognosis:

•

Lipomatosis is benign lesion with no effective therapy.

•

Surgical excision usually causes severe damage of the

involved nerve.

•

Division of the transverse carpal ligament may relieve

neurological symptoms.