BENIGN BONE TUMORS

OSTEOBLASTOMA

Definition:

Benign bone forming neoplasm producing woven bone

spicules bordered by prominent osteoblasts (osteoid

osteoma measuring more than 2.0 cm)

Epdemiology:

About 1% of bone tumors

Age: 10-30 y/o ( male teenagers)

Male:Female ratio 2.5:1,

Sites of involvement:

Predilection for the spine (40-55% of cases)

Other common sites femur and proximal tibia

Cementoblastoma of jaw is considered osteoblastoma

and is attached to the root of tooth.

Clinical findings:

Osteoblastoma of spine may cause back pain, scoliosis

and nerve root compression.

Jaw lesion may produce tooth pain.

Aspirin does not relieve pain after long therapy.

Imaging:

Lytic well circumscribed oval or round defect

Almost always confined by a periosteal shell of reactive

bone.

Gross:

Red or red brown (vascular).

Often with gritty or sandpaper consistency.

Histopathology:

Composed of woven bone spicules or trabeculae lined by

a single layer of osteoblasts.

Stromal rich vascularity.

Scattered osteoclast-type multinucleated giant cells are

often present.

Focal blood filled spaces mimicking Aneurysmal Bone

Cyst (ABC) may be present.

Osteoblastomas do not infiltrate and isolate pre-existing

lamellar bone structures as does osteosarcoma.

Prognosis:

Excellent

Recurrences unusual if well excisded

SIMPLE (UNICAMERAL ) BONE CYST (UBC)

Definition:

- Intramedullary, usually unilocular, bone cyst filled with

serous or sero-sanguineous fluid.

Epidemiology:

85% of patients in the first decades of life.

- Male:Female ratio 3:1.

Sites of involvement:

Most common locations:

proximal humerus

proximal femur

proximal tibia

Clinical findings:

Pain and swelling.

Patients may present with pathological fracture.

Imaging:

Well demarcated and radiolucent.

Typically begins in the metaphysis and extends into the

diaphysis.

Gross:

Fragments of thin whitish membrane

Usually during surgery you get scant tissue material.

Histopathology:

- Cyst wall consist of a thin layer of fibrous tissue

composed of scattered fibroblasts and collagen

fibers,.

No cell lining of cystic internal surface.

Pathologic fractures may cause reactive changes and

show numerous reactive fibroblasts, osteoclast type

giant cells, hemosiderin deposists and reactive woven

bone.

Genetics:

- Rearrangements involving chromosomes 4, 6, 8, 16, 21.

Prognosis:

Recurrence is reported at 10-20% of cases, especially in

children.

Growth arrest of the affected bone and avascular

necrosis of the head of the femur after pathological

fracture can occur

ANEURYSMAL BONE CYST (ABC)

Definition:

- Benign multiloculated , blood-filled cystic mass that is

often expansile and destructive.

Epidemiology:

- Affects all age groups but generally occurs during the

first two decades of life (median age approximately

13 years).

- No sex predilection.

Sites of involvement:

May affect any bone.

Usually arise in the metaphysis of long bone especially

the femur, tibia and humerus.

Clinical findings:

- Pain and swelling which may be secondary to fracture.

Imaging:

Usually eccentric, expansile lesion with well defined

margins.

Most lesions are completely lytic and often contain a

thin shell of reactive bone at the periphery.

CT and MRI may demonstrate internal septa and

characteristic fluid-fluid level.

Gross:

Well-defined sponge-like mass.

Composed of multiple, blood filled spaces separated by

thin, tan-white septa.

Histopathology:

Walls of ABC consist of plump uniform fibroblaststs

( which may be mitotically active), multinucleated

osteoclast-like giant cells ( sometimes they look like

jumping into swimming pool cystic spaces), and thin

trabeculae of reactive woven bone.

Surface of reactive woven bone is lined by plump

osteoblasts.

1/3 of cases contain a cartilage-like matrix, called 'blue

bone', which is not common in other bone lesions.

Necrosis is uncommon unless there has been a

previous pathologic fracture.

Genetics:

- Rearrangements of chromosome 17q13.

Prognosis:

- Recurrence rate following curretage is variable

(20-70%).

- Primary aneurysmal bone cysts account for

approximately 70% of all cases.

- Majority of secondary ABC arise in association

with benign neoplasms, most commonly giant

cell tumor of bone (GCT), chondroblastoma,

osteoblastoma, and fibrous dysplasia, and less

frequently, osteosarcoma.

FIBROUS DYSPLASIA

Definition:

Benign medullary fibro-osseous lesion which may involve

one (monostotic) or more bones (polyostotic).

Epidemiology:

Children and adults

Monostotic solitary lesion most common 70-80%

No sex predilection.

Sites of involvement:

Gnathic (jaw) bones most common

Long bones are more often involved in woman

Ribs and skull are favored sites for man.

Monostotic form, about 35% involve the head, 1/3 tibia and

femur, and rest 20% ribs.

Polyoostotic form, the femur, pelvis and tibia are more

common involved

Clinical findings:

Fibrous dysplasia may present in monostotic or polyostotic

form.

Polyostotic form can be confined to one extremity or one

side of the body or be diffuse.

Polyostotic form often manifest earlier in life than the

monostotic form.

FD is often asymptomatic but pain and fractures may be

part of clinical spectrum.

FD may be associated with oncogenic osteomalacia.

FD may be associated with McCune-Albright syndrome, in

which there are endocrine abnormalities and skin

pigmentation.

Imaging:

Non agressive geographical lesion with a ground glass

matrix.

In the appendicular skeleton, the margins are usually well

defined and surrounded by a rim of sclerotic bone.

FD in the craniofacial skeleton seems to be less well

defined and blends with surrounding bone.

Gross:

Well circumscribed

Gritty and leather-like consistency.

Histopathology:

Composed of cellular fibrous tissue surrounding irregular,

curvilinear bony trabeculae.

The bony trabeculae are discontinuous and are composed

of woven bone that is formed directly from the spindle cells

with minimal osteoblastic rimming.

In craniofacial tumors, the lesional bone tends to fuse with

the surrounding host cancellous bone, explaining the lack

of demarcation radiographically.

The spindle cells may be arranged in a storiform pattern,

and may be associated with collectioon of foamy

macrophages mimicking a xanthoma or fibroxanthoma.

Collagen fibers (Sharpey-like fibers) are frquently seen

extending from the fibrous tissue ibnto the lesional bone.

Cystic changes mimicking ABC are occasionally

encountered.

Genetics:

- Mutation of the G protein (guanine nucleotide-binding

protein).

Prognosis:

Good.

Therapy ranges from observation to surgical removal.

OSTEOFIBROUS DYSPLASIA

Definition:

Self-limited benign fibro-osseous lesion of bone.

Involving cortical bone of the anterior mid-shaft of the tibia

during infancy and childhood.

Epidemiology:

Rare tumor that accounts for less than 1% of all bone

tumors.

- Commonly seen in boys during the first two decades of

life with precipitous drop-off thereafter.

Sites of involvement:

Proximal or middle-third of the tibia is the most frequent

(90%)

Less common sites are ulna and radius.

Clinical findings:

Rare after the age of 15.

Most common presenting symptoms are swelling or

painless deforming (bowing) of the involved segment of

the limb.

Imaging:

Well-delineated, intracortical lucency, surrounded by

areas of sclerosis.

May form as a single lytic lesion, but more commonly

forms confluent oval-shaped, scalloped, saw-toothed or

bubbly multiloculated lytic lesions in cortex.

Gross:

Varies in size from <1 cm to >10cm.

Typically solid, yellow or white and gritty, and confined to

the cortex, which is expanded and attenuated.

Histopathology:

Composed of irregular curvilinear trabeculae of woven

bone that at the periphery merge with pre-existing

cancellous bone.

Trabeculae of woven bone are rimmed by prominent

osteoblasts and scattered osteoclasts may be seen.

intervening stroma is composed of benign appearing

spindle-shaped cells embedded in a collagenous matrix.

Isolate single stromal cells may express keratin; however,

clusters of epithelial cells, as seen in well differentiated

adamantinoma are absent.

Immunohistochemistry:

- Positive for vimentin, occasionally S100 and Leu7.

Genetics:

- Trisomy 7 and 8 have been demonstrated.

Prognosis:

Natural history of osteofibrous dysplasia is that of gradual

growth during the first decade of life with stabilization at

about 15 years of age resolution.

Progression of OFD-like adamantinoma to classic

adamantinoma has been shown in few patients.

FIBROUS CORTICAL DEFECT/NON-OSSIFYING FIBROMA

Definition:

Benign lesion of bone composed of spindle-shaped

fibroblasts, arranged in a storiform pattern, with a variable

admixture of multinucleated osteoclast-like giant cells.

Foamy cells (xanthoma), chronic inflammatory cells and

hemosiderin may be present

The name fibrous cortical defect is used when the lesion

is confined to the cortex; however if becomes large

enough to extend into adjacent medullary cavity than the

term non-ossifying fibroma is used.

Epidemiology:

Patient have ranged in age from 6 to 74 years old. 30-40%

in children.

An average age of 4 years 54% of boys and 22% of girls,

had a lesion involving the cortex, and most regressed

spontaneously over a period of approximately 2.5 years.

Site of involvement:

Approximately 40% of NOF occur in the long bones, with

distal femur, distal and proximal tibia most frequently

involved.

As many as 25% of cases involve the pelvic bone, in

particular the ilium.

Clinical findings:

Majority of NOF cases are asymptomatic, and are an

incidental discovery on X-rays performed for other reasons.

Larger lesion may cause pain that is probably secondary

to microfractures or obvious pathologic fracture.

Most pathologic fractures develop through lesions that

involve more than 50% of the diameter of the bone.

The vast majority of NOF are single, although thay are

multiple in 8% of cases.

Multiple NOF may be associated with syndromes such as

neurofibromatosis and Jaffe-Campanacci syndrome.

Imaging:

Eccentric, lytic lesions centered within the metaphyseal

cortex and adjacent medullary cavity of long tubular bones.

Well demarcated with sclerotic margins and frequently

harbor internal trabeculation.

Gross:

Eccentric, well circumscribed and have sclerotic borders.

The overlying cortex is thinned and may be completely

eroded.

The lesions are tan brown and frequently have areas that

are soft and yellow.

Histopathology:

Stroma of spindle-shaped fibroblasts, arranged , at least

focally, in a whorled, storiform pattern,among which

variable number of small, multinucleated, osteclast-type

giant cells are scattered.

Foam (xanthoma) cells, with small, dark nuclei are

frequently, but not always found interpersed among the

stromal cells individually, or in small clusters.

Scattered inflammatory cells, mainly lymphocytes, are

present.

Small stromal hemorrhages and hemosiderin may be

present.

Prognosis:

Excellent.

Asymptomatic NOF usually do not need surgical excision.

Painful larger lesions or those that have an impending or

established pathologic fracture are adequately treated by

curretage.

MYOFIBROMA

Definition:

Myofibroma and myofibromatosis are terms used to

denote the solitary (myofibroma) and multicentric

(myofibromatosis) occurence of benign neoplasms

composed of contractile myoid cells arranged around

thin-walled blood vessels.

Myofibroma(tosis) forms a morphological continuum

with myopericytoma and so-called infantile.

hemangiopericytoma.

Epidemiology:

Myofibroma of bone affects very young children and

many patients first develop lesions in utero.

Many cases are detected at birth or within first two

years of life.

Male predominance.

Sites of involvement:

Commonly involve the skull, jaw, ribs and pelvis.

Lesions of the appendicular skeleton are less frequent

and usually involve the metaphyses of bones.

Clinical findings:

- May be asymptomatic, produce palpable mass or

cause pain and even a pathologic fracture.

Imaging:

- Oval or elongate and lucent, with well circumscribed,

sclerotic margins and may expand the bone.

Gross:

- Firm, tan-white and well delineated.

Histopathology:

Central regions are usually densely cellular and

composed of sheets of small round cells with a

prominent vascular tree that has a

hemangiopericytoma-like pattern.

Mitotic activity, necrosis, and dystrophic calcification

are common findings.

This region merges peripherally with a component

composed of intersecting fascicles of plump spindle

cells that have blunt ended nuclei and conspicuous

eosinophilic cytoplasm, which resemble smooth

muscle cells.

Immunohistochemistry:

Myofibroblastic and more primitive component are

positive for vimentin and smooth muscle

actin, while the myofibroblastic component is more

strongly positive for pan-actin HHF-35.

Prognosis:

Depends on whether there is one or multiple lesions

and importantly, if there is visceral involvement.

The prognosis of bone lesions is excellent, and simple

excision is usually curative.

Patients with multiple visceral lesions, especially those

with involvement of the gastrointestinal tract may have

a fatal outcome from severe hemorrhage.

DESMOPLASTIC FIBROMA

Definition:

Rare, locally aggresive, solitary tumor microscopically

composed of well differentiated

myofibroblasts with abundand collagen production.

Epidemiology:

Rare, 0.1% of all primary bone tumors.

It tends to occur in adolescent and young adults with

near equal gender distribution.

Sites of involvement:

- May involve any bone but is most frequent in

mandible.

Clinical findings:

Pain and swelling of the affected area are the most

common symptoms.

Pathologic fracture or deformity of the affected bone can

occasionally be presenting symptom.

Imaging:

Usually well defined, radiolucent lesion that may expand

host lesion.

Interlesional trabeculation is frequent.

Larger lesion often show destruction of overlying cortex

with extension into soft tissue.

Features of more aggressive growth pattern with

irregular, ill-defined margins and pathological fracture

may be present.

Honeycombed or moth-eaten patterns have been

described.

Erosive, destructive pattern may mimic other, more

aggressive lesions.

DF has low signal intensity in both T1 and T2 weighted

MRI images.

Histopathology:

Composed of spindle cells (fibroblasts/myofibroblasts)

within an abundant, dense matrix of collagen.

Degree of cellularity is variable but cellular atypia and

pleomorphism are minimal or absent.

Mitoses are rare.

Exhibits an infiltrative destructive growth pattern with

permeation of bone marrow spaces and haversian

canals.

Borders of the tumor, especially in soft tissue, are

irregular with fingerlike projections infiltrating adipose

tissue and skeletal muscle.

Genetics:

- Trisomies 8 and 20 detected.

Prognosis:

DF exhibits locally aggressive behavior without capacity

to metastasize.

Recurrence following curretage and resection are 72%

and 17% respectively.

Local relapse has been reported as late as eight years

following primary surgery.

CHEST WALL HAMARTOMA/CHONDROMATOUS HAMARTOMA OF THE CHEST WALL

Definition:

Known as vascular-cartilaginous hamartoma, vascular

hamartoma of infancy, mesenchymal

hamartoma of chest wall, and chondromatous hamartoma

of the chest wall, is a rare mesenchymal

tumor that usually develops during fetal life or the first

year of infancy.

Epidemiology:

Fetal life or the first year of life.

Males are affected slightly more than females.

Sites of involvement:

- Arises from one or multiple ribs.

Clinical findings:

- May be asymptomatic or cause chest wall deformities or

respiratory distress.

Imaging:

Usually manifest as a large expansile mass that has

well-defined sclerotic margins.

Tumor erodes the cortex and extends into extrapleural

soft tissues, but is delineated by subperiosteal reactive

bone.

Intralesional radio densities are often present and may

consist of calcified cartilage that manifest as pop-corn

like speckled foci and mineralized bone that may

produce irregular trabeculations through the mass.

Hemorrhagic cystic cavities with flui-fluid levels

(secondary aneurysmal bone cyst like regions) are

common, and are seen by CT and T2-weighted MRI.

Gross:

Frequently large and range in size from 5-16 cm in

diameter.

Well circumscribed and consist of an admixture of firm,

gray-white, glistening, focally gritty, solid areas, and

numerous blood-filled cystic spaces.

Histopathology:

Composed of different tissue components including

nodules of hyaline cartilage surrounded by

proliferating fibrovascular tissue, newly deposited bone

and variably sized cysts.

Cystic spaces, which may dominate the mass, are filled

with blood and the walls are composed of fibrous tissue,

reactive bone and scattered osteoclast type giant cells.

Hyaline cartilage is moderately to densely cellular with

chondrocytes frequently organized in a pattern that

resembles growth plate.

At the periphery the matrix frequently undergoes

enchondral ossification.

Prognosis:

Excellent as recurrence is rare, and likely results from

incomplete resection.

Main postsurgical complication has been scoliosis

OSTEOCHONDROMA (EXOSTOSIS)

Definition:

Cartilage capped bony projection arising on the external

surface of bone containing a marrow

cavity that is continuous with that of the underlying bone.

Epidemiology:

Most common bone tumor.

Osteochondroma may be solitary or multiple, the latter

occuring in the setting of hereditary multiple exostoses.

Solitary lesions account for 80% of cases, and most

affected patients are diagnosed in their second decade of

life

- Male preponderance with a male to female ratio 1.5-2:1.

Hereditary multiple exostoses (HME) is an autosomal

dominant genetic disorder , and has prevalence of

1 per 50 000 in the general population making it one of

the more common inherited skeletal disease.

Patients with HME come to medical attention at the

younger age , usually during first decade, because they

cause severe skeletal deformities and are frequently

polyostic.

Sites of involvement:

Generally arise in bones performed by cartilage.

Most common site of involvement is the metaphyseal

region of distal femur, uppr humerus, upper tibia and fibula.

Clinical findings:

Many, if not most lesions, are asymptomatic and found

incidentally. In symptomatic cases, the symptoms are

often related to the size and location of the lesion.

Most common presentation is that of a hard of long-

standing duration.

Imaging:

Bulbous lesions on X rays, and they a narrow or broad

(sessile) osseous radiosense stalk, which is attached to

the underlying bone.

The characteristic feature is a projection of the cortex in

continuity with the underlying bone.

Excessive cartilage type flocullent calcification should

raise the suspicion of malignant transformation.

CT scan or MRI images typically show continuity of the

marrow space into the lesion. A thick cartilagenous cap

rises suspicion of malignant transformation.

Gross:

May be sessile or pedunculated.

The cortex and medullary cavity extends into the lesion.

The cartilage cap is usually thin.

A thick an irregular cap (greater than 2 cm) may be

indicative of malignant transformation.

Histopathology:

Lesion has three layers - perichondrium (fibrous layer

covering cartilage), cartilage and bone.

Outer layer is a fibrous perichondrium that is continuous

with the periosteum of the underlying bone.

Below this is a cartilage cap that is usually less than 2

cm thick (and decreases with age).

Within the cartilage cap the superficial chondrocytes are

clustered, whereas the ones close to bone resemble

growth plate.

-Loss of the architecture of cartilage, wide fibrous bands,

myxoid change, increased chondrocyte cellularity, mitotic.

activity, significant chondrocyte atypia and necrosis are all

features that may indicate secondary malignant

transformation.

Genetics:

- Abberations involving 8q22-24.1, EXT1 gene.

Prognosis:

Excision is usually curative.

Recurrence is seen with incomplete removal.

ENCHONDROMA AND ENCHONDROMATOSIS

Definition:

Benign hyaline cartilage neoplasm of medullary bone.

Enchondromatosis, is defined as two or more

enchondromas, and occurs in two clinical settings: 90% are

associated with Ollier disease (two or more enchondromas)

10% are seen in Maffuci syndrome (enchondroma +

hemangiomas)

Epidemiology:

Relatively common, accounting for 10-25% of all benign

bone tumors.

Age distribution is wide, ranging from 5-80 years.

Majority of patients present within the second through

fourth decades of life.

Solitary enchondromas are rare in young children, whereas

multiple enchondromas are encountered more frequently.

-Sexes are equally affected.

Sites of involvement:

Usually metaphyseal-diaphyseal in location and frequently

affect the short tubular bones of the hands.

Followed by bones of the feet and the long tubular bones,

especially proximal humerus and proximal and distal femur.

Clinical findings:

In the small bones of the hands and feet typically present

as palpable swellings, with or without pain.

Because they often expand these small bones and

attenuate the cortex, they frequently present with

pathological fractures.

Long bone tumors are more often asymptomatic, and are

detected incidentally in radiographs or bone scans taken for

other reasons.

Imaging:

Well marginated tumors that vary from radiolucent to

heavily mineralized.

Mineralization pattern is characteristic, consisting of

punctatae, flocullent, or ring and arc pattern.

Long bone tumors are usually centrally located within

metaphysis.

Diaphyseal long bone tumors are less common, and

epiphyseal tumors are rare.

Enchondromas in the small tubular bones can be centrally

or eccentrically located, and larger tumors may completely

replace medullary cavity.

More extensive endosteal erosion is considered suspicious

for low grade chondrosarcoma.

Cortical destruction and soft tissue invasion should never

be seen in enchondromas and would be most consistent

with chondrosarcoma.

Gross:

Most enchondromas measure less than 3cm and tumor

larger than 5 cm are uncommon.

They frequently have multinodular architectures, comprised

by nodules of cartilage separated by bone marrow.

Multinodular pattern appears more common in long bones

compared to confluent growth pattern in small tubular

bones.

Histopathology:

Nodules of hyaline cartilage that are well demarcated by

the surrounding bone and frequently undrego enchondral

ossification.

Cartilage shows hypo to moderate cellularity and contains

chondrocytes of variable size.

Condrocyte nuclei tend to be small, round and

hyperchromatic.

Scattered binucleated cells may be found.

Irregular purple granules within the matrix represent

calcifications.

Chondromas of Ollier disease are histologically similar to

those of sporadic solitary tumors; however, they frequently

demonstrate a greater degree of cellularity, cytologic

atypia, and may contain myxoid stroma, which may be

confused with diagnosis of chondrosarcoma.

Genetics:

- Structural abnormalities involving chromosomes 6

and12 have been detected.

Prognosis:

Solitary enchondromas successfully treated by intralesional

curretage in most cases, and local recurrences are

uncommon.

Clinical behavior of Ollier disease is unpredictable and there

is no specialized treatment.

Most dangerous complication is malignant transformation of

an enchondroma in Ollier disease. This occurs in 25-30%

of affected patients.

Patients with Ollier disease must have lifetime monitoring of

their tumors.

CHONDROBLASTOMA

Definition:

Benign, cartilage producing neoplasm usually arising in the

epiphyses of skeletally immature patients.

Epidemiology:

Accounts for less than 1% of primary bone tumors.

Most patients are between 10 and 25 years of age at

diagnosis and there is a male predominance.

Patients with skull and temporal bone involvement tend to

present at an older age (40-50 years).

Sites of involvement:

Usually arises in the epiphyses of the distal and proximal

femur, followed by the proximal tibia and proximal

humerus.

Patients with tumors arising in the flat bones, vertebrae and

short tubular bones tend to be older and skeletally mature,

although rare cases have been reported in children.

Clinical findings:

Majority of patients complain of localized pain, often mild,

but sometimes of many years duration.

Soft tissue swelling, joint stiffness and limitation, and limp

are reported less commonly.

Minority of patients may develop joint effusion, especially

around the knee.

Imaging:

Typically lytic, centrally or eccentrically placed, relatively

small lesions (3 to 6 cm), occupying less than one half of

the epiphysis.

Sharpely demarcated, with or without a thin sclerotic

border.

The presence of sclerotic rim, along with the younger age

of the patient, helps to differentiate chondroblastoma from

giant cell tumor of bone, which generally lacks sclerotic

border and occurs in patients less than 20 years.

Often helpful, matrix calcifications are only visisble in about

1/3 of patients.

Gross:

- Gritty and grayish white with areas of hemorrhage.

Histopathology:

Denselly cellular composed of an admixture of

mononuclear chondroblasts and multinucleated osteoclast-

type giant cells.

Chondroblasts grow in sheets, have eosinophilic

cytoplasm, well defined cell borders, and eccentrically

placed reniform or coffe-bean shaped nuclei.

Matrix generally consist of poorly formed matrix cartilage,

which mineralization may form 'chicken-wire' pattern

around single cells.

Mitotic activity and necrosis are commonplace.

Osteoclast-type giant cells are scattered throughout the

tumor but are most numerous in areas of matrix production

and hemorrhage.

Immunohistochemistry:

Chondroblasts express S-100 and vimentin but may also

stain for keratin and epithelial membrane antigen.

Genetics:

- Structural anomalies involving chromosomes 5 and 8.

Prognosis:

80-90% of chondroblastomas are successfully trated by

simple curretage with bone grafting.

Local recurrence rates range between 14-18% and occur

usually within two years.

Rare development of pulmonary metastases in

histologically benign chondroblastoma is well documented,

however this metastases are clinically non-progressive and

can often be satisfactorily treated by surgical resection

and/or simple observation.

LANGERHANS CELL HISTIOCYTOSIS (EOSINOPHILIC GRANULOMA) OF BONE

Definition:

Previously known as histiocytosis X, is an intraosseous mass of

proliferating Langerhans cells.

Langerhans cells are dendritic cells that normally populate the

skin, mucosal surfaces, lymph nodes and other tissues where

they function as specialized antigen presenting cells.

In Lngerhans cell histiocytosis, the proliferating cells are

monoclonal, supporting the theory that the disease is

neoplastic.

Epidemiology:

LCH is relatively rare disorder, accounting for less than 1% of all

osseous lesions.

Age distribution is ranging from the first month to 8th decade of

life with 80-85% of cases seen in patients under the age of 30,

and 60% under the age of 10.

Males are affected twice as often as females.

Sites of involvement:

Any bone may be involved, although there is predilection for LCH

to involve the bones of the skull, notably the calvarium.

Other frequently involved sites include the femur, the bones of

the pelvis, and the mandible.

Clinical findings:

Pain and swelling of the affected area occur most commonly.

In cases of temporal bone involvement , the presenting features

can show significant clinical overlap with otitis media and

mastoiditis.

Mandibular involvement , loosening or loss of teeth can be

encontered.

Vertebral body involvement may result in compression fracture

and possible neurological impairment. LCH is associated with

variety of clinical syndromes.

Single or multiple lesion restricted to skeleton have been termed

eosinophilic granuloma.

Multifocal bone disease associated with exophthalmos and

diabetes insipidus is known as Hand-Shuller-Christian disease,

and Letterer-Siwe disease is an aggressive disseminated form

of the disorder that occurs in infants.

Letterer-Siwe disease usually affects very young childrens less

than 2 y/o, whereas, Hand-Schuller-Christian disease and

eosinophilic granuloma are seen in older children and young

adults.

Imaging:

LCH lesions are well defined and lytic on radiographs, however,

in a minority of cases may have ill-defined and permeative

margins.

Cortical involvement may elicit a periosteal reaction.

Complete resolution of radiographic abnormalities may follow

treatment or occasionally occurs spontaneously.

Gross:

- Involved tissue is soft and is red in color.

Histopathology:

Proliferating Langerhans cells are ovoid or round histiocyte-like

cells that are arranged in aggregates, sheets, or individually

within a loose fibrous stroma.

The cells have eosinophilic cytoplasm and contain central ovoid

'coffe bean' shaped nuclei with typical nuclear grooves.

Chromatin is either diffusely dispersed or condensed along the

nuclear membranes.

Langerhans cells are frequently admixed with inflammatory cells

including large numbers of eosinophils, as well as lymphocytes,

neutrophils and plasma cells.

Necrosis may be found in minority cases and if is prominent, is

usually complication of a pathologic fracture.

Mitotic figures may be seen; however atypical forms are absent.

Immunohistochemistry:

- Langerhans cells are positive for CD1a, S100 and negative

for CD68 and CD45.

Electron Microscopy:

- Intracytoplasmic 'tennis racket' shaped inclusions known as

Birbeck granules.

Prognosis:

Treatment and prognosis of LCH depends on the site and size of

the lesion, the age of the patient, and the presence or absence

of multifocal disease.

Monostotic disease is usually managed by curettage, however

tumors located in areas difficult to excise may be treated with

low dose radiation therapy.

Single or multiagent therapay may be administered in the

setting of disseminated disease.

ROSAI-DORFMAN DISEASE

Definition:

- Sinus histiocytosis with massive lymphadenopathy (Rosai-

Dorfman disease) is a rare, proliferative, histiocytic disease

characterized by the enlargement of lymph node sinuses

caused by an aggregation of histiocytic cells that exhibit

marked lymphophagocytosis (numerous phagocytized

lymphocytes are present in cytoplasm).

- Primary or secondary involvement of extranodal sites,

including the skeleton, is frequent.

Epidemiology:

Majority of patients are teenagers and young adults.

Mean age 20 years.

No gender predilection.

Soliatary RDD in bones was described in young childrens.

Clinical findings:

Fever and massive cervical lymphadenopathy are the most

frequent symptoms at presentation.

Other symptoms include weight loss, malaise and night

sweats.

Quite often the disease fully manifests after a short period of

a nonspecific fever and pharyngitis.

Imaging:

Skeletal involvement manifests by the presence of solitary or

multifocal defects with poorly or well-demarcated borders.

RDD lesions are intramedullary and are associated with

cortical erosion, complete cortical disruption, elevation of

the periosteum, or a combination of these features.

Radiographic manifestations and clinical symptoms suggest

an inflammatory disorder, such as osteomyelitis.

Histopathology:

In typical cases, the sinuses of lymph nodes are filled with

histiocytic cells.

These cells have prominent eosinophilic cytoplasm,

indistinct borders, and round or oval nuclei with a very fine

chromatin pattern and a single small nucleolus.

Nuclear grooves are not present, and some of these cells

may have several nucleoli.

Occasional cells with multilobulated nuclei may be present.

Mitotic figures are rare, atypical mitoses are not present.

The most striking and diagnostically important feature of

histiocytic cells is prominent emperipolesis or

lymphophagocytosis (i.e. the presence of well-preserved

lymphocytes within their cytoplasm).

In addition to lymphocytes, a smaller number of

phagocytized plasma cells, neutrophils, and red cells is

also present.

Extranodal disease has all these features except that

histiocytic cells, instead of growing in sinuses, form

irregular

geographic areas separated by other inflammatory cells.

Involvement of skeletal system has the same features.

Immunohistochemistry:

- Histiocytic cells in RDD are S 100 positive and CD1a

negative.

Prognosis:

Rosai-Dorfman disease is considered a histologically

benign, proliferative, histiocytic disorder with a variable, but

occasionally fatal, outcome.

The majority of patients have indolent regressive or clinically

stable disease after several years of follo-up.

Fatal outcome of the disease is associated with the severe

involvement of extranodal sites (lungs and kidney).

HEMANGIOMA OF BONE

Definition:

Hemangioma is benign solitary tumor composed of newly

formed vessels of capillary or cavernous type.

Epidemiology:

Wide age distribution, ranging from the first to eight decades

of life, with nearly 70% of the cases diagnosed in patients

between 30 and 60 years.

Occasionally hemangiomas become clinically evident during

the first decade of life. There is no sex predilection.

They are rare in newborns and infants and reported cases

have arisen in the skull bones.

The tumors are usually solitary, but multifocal neoplasms

have been described most frequently in the vertebral

columns.

Sites of involvement:

Hemangiomas frequently occur in craniofacial bones ,

predominantly in calvarium (50%), followed by the

spine (20%).

Clinical findings:

- Relatively common asymptomatic.

Imaging:

Hemangiomas present as lucent, well demarcated defects.

In flat bones, they markedly expand the bonecontour and

produce rarefaction with radially oriented striations.

Vascular nature of the lesion often is suggested by its bubbly

or honeycomb trabeculated appearance.

Overlying cortex is expanded and thinned, but complete

cortical disruption and invasion into soft tissue are not

present.

Chracteristic sunburst appearance of hemangioma is seen in

skull lesion (not confuse with that seen in osteosarcoma of

long bones).

Smaller lesions may present as intracortical rarefaction with

or without a honeycombed appearance and adjacent

sclerosis.

MRI of hemangiomas generally reveals a low signal on T1-

weighted images and a high signal on T2 weighted images

(fluid content of tumor vessels).

Gross:

Brown-red or dark red, well demarcated, medullary lesion.

It may have a honeycomb appearance with sclerotic bone

trabeculae interspersed among hemorrhagic cavities.

Histopathology:

Hemangiomas are composed of conglomerate of thin-walled

blood vessels.

Vessels can have dilated open channels (cavernous

hemangioma) or less frequently may be composed of

capillary-sized vessels (capillary hemangioma).

Majority of bone hemangiomas are of cavernous or mixed

types.

Vascular channels are lined by a single layer of flat

endothelial cells.

Intercellular tissue is composed of loose connective tissue

that may show myxoid change.

Bone may be completely resorbed in affected area.

Vascular channels of hemangioma are complete, separate

and do not show anastomosing pattern.

Prognosis:

Asymptomatic small hemangiomas require no treatment;

some may undergo spontaneous regression.

Symptomatic lesions or those that are large and may cause

pathologic fracture or vertebral collapse require treatment.

Curretage and bone grafting usually is sufficient.

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OSTEOID OSTEOMA

Definition:

Benign bone-forming tumor.

Similar to osteoblastoma but smaler size (1.5 - 2.0 cm).

Epidemiology:

- Children and adolescent.

Sites of involvement:

Most common in long bones, femur/tibia (cortex of

metaphysis)

May be found in any bone.

Clinical findings:

- Intense localized pain particularly at night.

- Pain relieved by aspirin, NSAIDs or surgery.

Imaging:

Small, round lucency.

Variable mineralization surrounded by extensive.

sclerosis.

Macroscopy:

- Small cortically based,

- Red, gritty round lesion

Histopathology:

Limited growth pattern (1.5- 2.0 cm).

Sharp circumscription near cortical surface (forming nidus).

Composed of anastomosing bony trabeculae with variable mineralization.

Bony trabecules lined by plump osteoblast.

Vascularized connective tissue: surrounded by sclerotic bone.

Benign giant cells may be present.

Genetics:

Described loss of 17q.

Prognosis:

Excellent, recurrences rare after surgical excision.

Differential Diagnosis:

Osteoblastoma

Osteomyelitis

GIANT CELL TUMOR

Definition:

Benign, locally aggressive neoplasm.

Composed of sheets of neoplastic ovoid mononuclear cells

interspersed with uniformly distributed large, osteoclastlike giant

cells.

Epidemiology:

Giant cell tumour represents around 4-5% of all primary bone

tumours.

Peak incidence is between the ages of 20 and 45.

10-15% of cases occur in the second decade.

Not commonly seen in adolescents, although cases were described.

There is slight female predominance described.

Sites of involvement:

Giant cell tumours typically affect the ends of long bones, especially

the distal femur, proximal tibia, distal radius and proximal humerus.

- About 5% affect flat bones, especially those of the pelvis.

Multicentric giant cell tumors are very rare and tend to involve the

small bones of the distal extremities.

Clinical findings:

Patients typically present with pain, swelling and often limitation of

joint movement

Pathological fracture is seen in 5-10% of patients.

Imaging:

X-rays of lesions in long bones usually show an expanding and

eccentric area of lysis.

Lesion normally involves the epiphysis and adjacent metaphysis.

Extension up to the subchondral plate, sometimes with joint

involvement may be present.

Rarely, the tumour is confined to the metaphysis,usually in

adolescents where the tumour lies in relation to an open growth

plate,but occasionally also in older adults.

Diaphyseal lesions are exceptional.

CT scanning gives a more accurate assessment of cortical thinning

and penetration than plain radiographs.

Gross:

- Tissue is usually soft and reddish brown, but there may be yellowish areas corresponding to xanthomatous change.

Firmer whiter areas represent fibrosis.

- Bloodfilled cystic spaces are sometimes seen and may mimick

aneurismal bone cyst.

Histopathology:

Tumor is composed of round to oval polygonal or elongated

mononuclear cells evenly mixed with numerous osteoclastlike giant

cells which may be very large and contain 50 to 100 nuclei.

The nuclei of the stromal cells are very similar to those of the

osteoclasts, having an open chromatin pattern and one or two small

nucleoli.

The cytoplasm is ill-defined, and there is little intercellular collagen.

Mitotic figures are invariably present, but no atypical mitoses

present.

It is now generally accepted that the characteristic large

osteoclastic giant cells are not neoplastic.

The mononuclear cells, which represent the neoplastic component,

are thought to arise from primitive mesenchymal stromal cells.

Areas of fibrosis may be present.

Secondary aneurysmal bone cyst change may occurs in 10% of

cases.

1/3 of cases, show presence of intravascular plugs, particularly at

the periphery of the tumour.

Areas of necrosis are common, especially in large lesions.

These may be accompanied by focal nuclear atypia which may

suggest malignancy

Genetics:

Telomeric association is the most frequent chromosomal aberration.

The telomeres most commonly affected are 11p, 13p, 14p, 15p, 19q,

20q and 21p.

Prognosis:

Giant cell tumour is capable of locally aggressive behaviour and

occasionally of distant metastasis.

Histology does not predict the extent of local aggression.

Local recurrence occurs in approximately 25% of patients, and is

usually seen within 2 years.

Pulmonary metastases may be seen in 2% of patients with giant

cell tumours, on average 3-4 years after primary diagnosis.

OSTEOMYELITIS

Definition:

Inflammation of bone and marrow also known as infection of bone

May manifest as a primary solitary focus of disease or as a complication of other systemic disease.

May be caused by different bacterial organisms

Types of osteomyelitis:

Pyogenic Osteomyelitis

Hematogenous osteomyelitis commonly occurs in children.

Staphylococcus aureus is the most common organism responsible for pyogenic osteomyelitis

H. inflenzae & group B streptococci are frequent pathogens in neonatal infection.

Gram negative organisms are isolated from patients with genitourinary infection or who are IV drug abusers

Almost always caused by bacteria.

Organisms reach to the bone by:
1 hematogenous spread
2 extension from a contiguous site
3 direct implantation

The latter (3) occurs as a complication of a compound fracture or of surgery.

Symptoms:

High fever, localized pain and swelling

Labs:

high white cell count, high ESR.

Most frequent site in children:

distal femur, proximal tibia

proximal humers and distal radius all of which are areas of rapid growth

Site of infection in the bone is influenced by high vascular supply

In neonate, the metaphyseal vessels penetrate the growth plate resulting in infection of metaphysis, epiphysis or both

In children metaphyseal localization.

In adult subchondral region or vertebral localization

Morphology:

Rupture of the periosteum leads to soft tissue abscess and draining sinus

In infants epiphyseal infection spread through the articular surface causing destruction of the cartilage leading to joint infection also known as septic or suppurative arthritis.

In vertebrae, the infection destrys the hyaline cartilage end plate and intervertebral disk and spreads to the adjacent vertebrae

Depends on stage (acute, subacute or chronic).

Bacteria localized in bone induce acute inflammation and cell death.

Bone necrosis in 48 hours and spread of infection to the periosteum via haversian system leading to periosteal elevation and subperiosteal abscess formation.

This process impairs the blood supply causing segmental bone necrosis, the dead piece of bone is known as Sequestrum.

Radiology:

Lytic focus of bone destruction with peripheral zone of sclerosis and reactive periosteum.

Hot spots on bone scan.

MRI: increased signal intensity in the medullary space.

D.D.: small round blue cell tumor

Chronic osteomyelitis:

One week after the infection, host response evolves with infiltration by chronic inflammatory cells and release of cytokines which in turn stimulates osteoclastic bone resorption, ingrowth of fibrous tissue and reactive new bone formation.

Reactive bone in the form of a living tissue around the segment of necrotic bone (sequestrum) is known as involucrum.

Variants of osteomyelitis:

Brodie abscess – small intraosseous abscess that frequently involves the cortex and is walled of by reactive bone. It may mimick tumor.

Sclerosing osteomyelitis of Garre affects the jaw bone with extensive new bone formation.

Chronic Recurrent Multifocal Osteomyelitis

Clinical course:

Blood culture may be positive

Antibiotics and surgical drainage are the usual treatment.

In 5% to 25% cases, the infection persists as chronic osteomyelitis.

Acute flare ups can occur after years of dormancy.

Rare complications: fracture, sepsis, scc in the sinus and bone sarcoma.