Snapshot A 12-year-old boy develops mild pain in his right leg. The pain is worse at night and improves with aspirin. A radiograph of the right leg is shown demonstrating a small mass with a radiolucent nidus surrounded by reactive bone. The patient is subsequently diagnosed with an osteoid osteoma. Osteoma Definition benign bone tumor (osteogenic) derived from osteoblasts Presentation location skull mandible symptoms painless mass associated conditions Gardner syndrome Associated findings histology proliferating osteoblasts with active intramembranous ossification radiography radiodense and smooth bony mass Osteoid Osteoma Definition benign bone tumor (osteogenic) derived from osteoblasts small (< 2 cm) Presentation location proximal femur (most common) tibial diaphysis vertebrae symptoms focal pain that resolves with NSAIDs if arising in the spine, may cause painful scoliosis Associated findings histology nidus of osteoid and immature osteoblasts surrounded by a rim of reactive bone formation radiography radiolucent nidus (< 2 cm) surrounded by reactive bone Osteoblastoma Definition benign but locally aggressive bone tumor (osteogenic) derived from osteoblasts larger than an osteoid osteoma (> 2 cm) Presentation location vertebrae (most common) long bone diaphyses symptoms focal pain that is not relieved by NSAIDs if arising in the spine, may cause neurologic symptoms Associated findings histology nidus of osteoid and immature osteoblasts surrounded by a rim of reactive bone formation radiography radiolucent nidus (> 2 cm) surrounded by reactive bone login to view 1 more bullet Giant Cell Tumor (Osteoclastoma) Definition benign but locally aggressive tumor derived from stromal cells with accompanying giant cells stromal cells resemble interstitial fibroblasts and are neoplastic cells giant cells are derived from monocyte/macrophage lineage and have similar characteristics to osteoclasts Presentation location metaphyseal regions of long bones login to view 3 more bullets symptoms focal pain login to view 1 more bullet Associated findings histology 3 cells types may be seen login to view 8 more bullets radiography an eccentric lytic metaphyseal lesion that may extend into the distal epiphysis characteristic "double bubble" or "soap bubble" appearance login to view 1 more bullet Osteochondroma (Exostosis) Definition benign cartilage-derived tumor (chondrogenic) containing bone and a cartilage cap arises as a lateral projection of the growth plate most common cartilage-derived tumor two forms solitary osteochondroma login to view 1 more bullet syndromatic osteochondromas login to view 1 more bullet Presentation location metaphyseal regions of long bones login to view 3 more bullets symptoms painless mass Associated findings histology normal bony trabeculae with a thin cartilaginous cap radiography sessile (broad base) or pedunculated (narrow stalk) lesions found on the surface of bones Enchondroma Definition benign cartilage-derived (chondrogenic) tumor arises when chondroblasts and epiphyseal cartilage escape from the physis, enter the metaphysis, and proliferate second most common cartilage-derived tumor two forms solitary enchondroma syndromatic enchondromas login to view 2 more bullets Presentation location medullary cavity in the metaphyseal or diaphyseal regions login to view 3 more bullets symptoms most often asymptomatic pathologic fracture Associated findings histology bland mature hyaline cartilage radiography well-defined lucent medullary lesion