IUHS Student-2-Student USMLE Step 1 Recall

                                                Musculoskeletal

                                           Bone/Cartilage Tumors

Osteomas

benign tumor almost excusively involves the skull and facial bones; the frontal sinus is the most commmon location...males are affected more often than females, and the lesion can occur at any age...

osteoma is predominantly a solitary lesion, multiple osteomas can occur in association with intestinal polyposis and soft tissue tumors...such as Gardners Syndrome...

Clinical features - asymptomatic unless it interferes with drainage from the paranasal sinus...

Pathology - originates from the periosteum...little evidence of osteoblastic activity...

Osteoid Osteoma

less than 2 cm in greatest dimension and usually occur in the teens and twenties...men out number women 2 to 1...have a predilection for the appendicular skeleton...50% of cases involve the tibia or femur...

central lucency surrounded by a sclerotic rim...

painful lesions...pain is caused by prostaglandin E2 production...characteristically nocturnal (pain) and is treated with aspirin...

Osteosarcomas (osteogenic sarcoma)

highly malignant bone tumor characterized by the production of osteoid and bone...most arise in the metaphyseal end of long bones...

atypical, elongated cells with hyperchromatic nuclei in an osteoid stroma...

male predominace...peaks in early teens...

Osteosarcomas are composed of spindle cells that make osteoid.

characterized by malignant anaplastic cells secreting osteoid...

Osteosarcomas are more likely to appear in the first to third decades of life

Incidence - most common primary malignant tumor of bone (next to multiple myeloma), accounting for approximately 16% of all bone malignancies

Etiology - unknow, or radiation and preexisting bone disorders, such as Paget's disease

Clinical Features - pain and swelling of the affected region...limitation of motion of the nearby joints..weight loss and secondary anemia, and subperiosteal elevation (Codman's triangle), and infiltration of adjacent soft tissue

Pathology - large necrotic and hemorrhagic mass...usually ends in epiphyseal cartilage...

composed predominantly of cells with a spindle shape and a high N/C ratio with marked pleomorphism. These cells are vimentin positive, cytokeratin negative, and CD45 negative by immunohistochemical staining

Osteochondromas

also known as an exostosis, is a benign cartilage-capped outgrowth that is attached to the underlying skeleton by a bony stalk...

male predominace...

it is a relatively common lesion and can be solitary or multiple...multiple osteochondromas occur in multiple hereditary exostosis, which is an autosomal dominant hereditary disease that is genetically heterogeneous...

osteochondromas usually arise from the metaphysis near the growth plate of long tubular bones, especially about the knee...

 Morphology - the outer layer of the head of the osteochondroma is composed of benign hyaline cartilage varying in thickness and is delineated peripherally by perichondrium...the cartilage has the appearance of disorganized growth plate and undergoes enchondral ossification with the newly made bone forming the inner portion of the head and stalk...

Clinically - present as slow growing masses, which can be painful if they impinge on a nerve or if the stalk is fractured...

Chondromas

chondromas are benign tumors of hyaline cartilage...they may arise within the medullary cavity, where they are known as enchondromas, or on the surface of bone, where they are called subperiosteal or juxtacortical chondromas...

enchondromas are the most common of the intraosseous cartilage tumors....enchondromas are usually solitary, located in the metaphyseal region of tubular bones, and the favored sites are the short tubular bones of the hands and feet...

the syndrome of multiple enchondromas or enchondromatosis is known as Ollier disease...if the enchondromatosis is associated with soft tissue hemangiomas, the disorder is called Maffucci syndrome...

 Morphology - enchondromas are usually smaller than 3 cm and grossly are gray-blue and translucent and have a nodular configuration...

characteristic "O-ring sign" (radiolucent central cartialge surrounded by a thin layer of bone)...

Chondrosarcoma

the feature common to them all is the production of neoplastic cartilage...

male predominance...

chondrosarcoma is subclassified according to site as intramedullary and juxtacortical and histologically as conventional (hyaline and/or myxoid), clear cell, dedifferentiated, and mesenchymal variants...

second most common malignant matrix-producing tumor of bone...patients with chondrosarcoma are usually in their forties or older...the clear cell and especially the mesenchymal variants occur in younger patients, in their teens or twenties...

the tumor affects men twice as frequently as women and has no race prediliction...

Chondrosarcomas can occur in association with osteochondromatosis (seen to arise in benign cartilagenous tumors)...

conventional chondrosarcoma is composed of malignant hylaine and myxoid cartilage...the large bulky tumors are made up of nodules of gray-white, somewhat translucent glistening tissue...

in predominantly myxoid variants, the tumors are viscous and gelatinous and ooze from the cut surface...

spotty calcification are typically present, and central necrosis may create cystic spaces...

the adjacent cortex is thickened or eroded, and the tumor grows with broad pushing fronts into the surrounding soft tissue...

malignant cartilage infiltrates the marrow space and surrounds preesixting bony trabeculae...

Atypical chondrocytes...They are most often central in location (axial skeleton or proximal long bones)...

commonly arise in the central portions of the skeleton, including the pelvis, shoulder, and ribs...

the clear cell variant is unique in that it originates in the epiphyses of long tubular bones...

in contrast to enchondroma, chondrosarcoma rarely involves the distal extremities...

these tumors usually present as painful, progressively enlarging masses...

Chondrosarcomas have a wide age range. Many are in older adults

Ewing Sarcoma

Ewing sarcoma is a primary malignant small round cell tumor of bone...it has long posed a difficult diagnostic problem b/c the tumors resemble those of lymphoma, rhabdomyosarcoma, neuroblastoma, and oat cell carcinoma...

current evidence indicates that Ewing sarcoma tumor cells exhibit a neural phenotype...the expression of the oncogene c-myc and the identification of a specific chromosome translocation in both Ewing sarcoma and similar tumors of soft tissue, called primitive neuroectodermal tumors (PNET), further support this contention...11;22 translocation...

thus, Ewing sarcoma and PNET of bone are closely related tumors that differ in their degree of differentiation...

tumors that demonstrate neural differentiation by light microscopy, immunohistochemistry, or electron microscopy are labeled PNETs, and those that are undifferentiated by these analyses are dianosed as Ewing sarcoma...

S-100 and neuron specific enolase are positive in Ewing Sarcoma...

Ewing sarcoma and PNET account for approximately 6-10% of primary malignant bone tumors and follow osteosarcoma as the second most common group of bone sarcomas in children...

Ewing sarcoma has the youngest average age at presentation as most patients are 10 to 15 years old, and approximately 80% are younger than 20 years...

boys are slightly more frequently affected than girls, and there is a striking predilection for whites; blacks are rarely afflicted...

usually arises in the diaphysis of long tubular bones, especially the femur (most often) and the flat bones of the pelvis...

it presents as a painful enlarging mass, and the affected site is frequently tender, warm, and swollen...

some patients have systemic findings, including fever, elevated sedimentation rate, anemia, and leukocytosis, which mimic infection...

plain x-rays show a destructive lytic tumor that has permeative margins...the characteristic periosteal reaction produces layers of reactive bone deposited in an onion-skin fashion...

treatment of Ewing sarcoma includes chemotherapy and surgery with or without radiation...the advent of effective chemotherapy has dramatically improved the prognosis from a dismal 5% to 15% to a 75% 5 year survival; at least 50% are long term cures....

to differentiate this lesion from lymphma nd neuroblastoma, PAS staining of glycogen positive, diastase sensitive cytoplasmic granules within the tumor cells of Ewing's sarcoma is characteristic...

Giant Cell Tumors

giant cell tumors is so named b/c it contains a profusion of multinucleated osteoclast type giant cells, giving rise to the synonym osteoclastoma...

spindle shaped cells with multinucleated giant cells...

giant cell tumor is a relatively uncommon benign, but locally aggressive neoplasm...

it usually arises during the twenties to forties...giant cell tumors are postulated to have a monocyte-macrophage lineage, and the giant cells are believed to form via fusion of mononuclear cells...

giant cell tumors in adults involve both the epiphyses and the metaphysis, but in adolescents they are confined proximally by the growth plate and are limited to the metaphysis...

the majority of giant cell tumors arise around the knee (distal femur and proximal tibia)...but virtually any bone may be involved...the location of these tumors in the ends of bones near joints frequently causes patients to complain of arthritic symptoms...

occasionally, they present as pathologic fractures...

"soap bubble" appearance describes giant cell tumor...or "double bubble"...