Ans. A. Osteosarcoma. (Ref. Pathology Robbings 8th/Table 21-2).a large, destructive, mixed lytic and blastic mass with indistinct infiltrating margins. The tumor frequently breaks through the cortex and lifts the periosteum, resulting in reactive periosteal bone formation ("Sun-burst" or 'Sunray' periosteal reaction). A triangular shadow on x-ray between the cortex and raised periosteum (Codman triangle) is characteristic of osteosarcomas. Osteosarcomas typically spread hematogenousiy;Osteosarcoma# Outside of myeloma and lymphoma, osteosarcoma is the most common primary malignant tumor of bone, accounting for approximately 20% of primary bone cancers;# Osteosarcomas occur in all age groups but some 75% of patients are younger than age 20, with a second peak occuring in the elderly, usually with other conditions, including Paget disease, bone infarcts, and prior irradiation.# Men are more commonly affected than women (1.6 : 1). Although any bone can be involved, most tumors arise in the metaphyseal region of the long bones of the extremities, with almost 60% occurring about the knee, 15% around the hip, 10% at the shoulder, and 8% in the jaw.# The most common type of osteosarcoma is primary, solitary, intramedullary, and poorly differentiated, producing a predominantly bony matrix.# Osteosarcoma typically present as painful enlarging mass, although a pathologic fracture can be the first symptom.Rx:# Despite aggressive behavior, standard Rx with chemotherapy and limb-salvage therapy currently yields long-term survivals of 60% to 70%.Tumors of Bone: Tumor TypeCommon LocationsAge (yr) Morphology Bone-Forming BENIGN 1.Osteoma(ivory, cancellous)Facial bones, skull40-50Exophytic growths attached to bone surface; histologically resemble normal bone2.Osteoid osteoma(most common benign bone tumor)Metaphysis of femur and tibia10-20Cortical tumors, characterized by pain (NIDUS); histologically interlacing trabeculae of woven bone3.OsteoblastomaVertebral column10-20Arise in vertebral transverse and spinous processes; histologically similar to osteoid osteoma MALIGNANT 1.Primary osteosarcomaMetaphysis of distal femur, proximal tibia, and humerus10-20Grow outward, lifting periosteum, and inward to the medullary cavity; microscopically malignant ceils form osteoid; cartilage may also be present2.Secondary osteosarcomaFemur, humerus, pelvis>40Complications of polyostotic Paget disease; histologically similar to primary osteosarcoma Cartilaginous BENIGN 1.Osteochondroma (most common benign bone tumor)Metaphysis of long tubular bones10-30Bony excrescences with a cartilaginous cap; may be solitary or multiple and hereditary2.ChondromaSmall bones of hands and feet30-50Well-defined single tumors resembling normal cartilage; arise with medullary cavity of bone; uncommonly multiple and hereditary MALIGNANT 1.ChondrosarcomaBones of shoulder, pelvis, proximal femur, and ribs40-60Arise within medullary cavity and erode cortex; microscopically well differentiated cartilage-like or anaplastic; Miscellaneous 1.Giant-cell tumor(usually benign)Epiphysis of long bone20-40Lytic lesions that erode cortex; microscopically, contain osteoclast-like giant cells and round to spindle-shaped mononuclear cells; majority are benign2.Ewing tumor(malignant)Diaphysis and metaphysis10-20Arise in medullary cavity; microscopically, sheets of glycogen-rich small round cells; aggressive neoplasm3.Chordoma(Locally malignant)Axial skeleton (Sacrococcygeal bones, Clivus, cCervical vertebra)20-40Expansile lytic tumor."Physalliferous cells" +