Table21.1ClassificationofSelectedPrimaryBoneTumors greatest frequency within the first three decades of life. In older adults, a bone tumor is more likely to be malignant.
Tumors in this category all produce unmineralized osteoid or mineralized woven bone.
Osteoid osteoma and osteoblastoma are benign bone-producing tumors that have similar histologic features but differ clinically and radiographically. Osteoid osteomas are, by definition, less than 2 cm in diameter, and are most common in young men. About 50% of cases involve the femur or tibia, wherein they typically arise in the cortex. Usually, there is a thick rim of reactive cortical bone that may be the only clue radiographically. Despite their small size, they present with severe nocturnal pain that is relieved by aspirin and other nonsteroidal anti-inflammatory agents. The pain is probably caused by prostaglandin E2 produced by osteoblasts. Osteoblastoma is larger than 2 cm and involves the posterior components of the vertebrae (laminae and pedicles) more frequently. The pain is unresponsive to aspirin, and the tumor usually does not induce a marked bony reaction. Osteoid osteoma is frequently treated by radiofrequency ablation, whereas osteoblastoma is usually curetted or excised. Malignant transformation is rare.
ofhemorrhagicgrittytantissue.Theyarewellcircumscribed
BoneformingBenignOsteoidosteomaMetaphysisoflong10–20Cortical,interlacingmicrotrabeculaebones ——OsteoblastomaVertebralcolumn10–20Posteriorelementsofvertebra,histologysimilartoosteoidosteoma
UnknownoriginBenignGiantcelltumorEpiphysisoflong20–40Destroysmedullaandcortex,sheetsbones ——AneurysmalboneProximaltibia,distal10–20Vertebralbody,hemorrhagicspacescystfemur,vertebra separatedbycellular,fibrousseptae
AdaptedfromUnniKK,InwardsCY:Dahlin’s Bone Tumors, ed6.Philadelphia,2010,Lippincott-Williams&Wilkins;bypermissionofMayoFoundation.
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Fig.21.15 ).Thestromasurroundingtheneoplasticboneconsistsoflooseconnectivetissuethatcontainsmanydilatedandcongestedcapillaries.Therelativelysmallsize,well-definedmargins,andbenigncytologicfeaturesoftheneoplasticosteoblastshelpdistinguishthesetumorsfromosteosarcoma.Osteoidosteomaselicittheformationofalargeamountofreactivebone,whichencirclesthelesion.
Osteosarcoma is a malignant tumor that produces osteoid matrix or mineralized bone. Excluding hematopoietic tumors (myeloma and lymphoma), osteosarcoma is the most common primary malignant tumor of bone. Osteosarcoma has a bimodal age distribution; 75% of osteosarcomas occur in persons younger than 20 years of age. The smaller second peak occurs in older adults, who frequently suffer from conditions known to predispose to osteosarcoma, such as Paget disease, bone infarcts, and previous radiation. These are referred to as secondary osteosarcomas. Overall, men are more commonly affected than women (1.6:1). The most common sites in adolescents are the metaphyseal regions of the distal femur and proximal tibia.
Osteosarcomas present as painful, progressively enlarging masses. Sometimes a pathologic fracture is the first indication. Radiographs usually show a large, destructive, mixed lytic and sclerotic mass with infiltrative margins (