--- BONE-FORMING TUMORS 1. Osteoma - Nature: Benign, slow-growing - Who: Adults, middle-aged - Where: Predominantly skull and facial bones (especially paranasal
--- BONE-FORMING TUMORS 1. Osteoma - Nature: Benign, slow-growing - Who: Adults, middle-aged - Where: Predominantly skull and facial bones (especially paranasal sinuses) - Histology: Dense, compact mature bone - Clinical: Usually asymptomatic, found incidentally. Multiple osteomas → think Gardner syndrome - X-ray: Dense, well-defined bony protrusion --- 2. Osteoid Osteoma - Nature: Benign - Who: Young males, 10–25 years - Where: Cortex of long bones — femur and tibia most common - Key feature: Nidus — a small ( females - Where: Posterior elements of the vertebral column (distinguishes it from osteoid osteoma) - Key feature: Essentially a large osteoid osteoma — nidus 2 cm - Clinical: Pain but NOT relieved by aspirin — that's a key distinguishing point from osteoid osteoma - X-ray: Expansile lytic lesion, less sclerosis than osteoid osteoma --- 4. Osteosarcoma - Nature: Malignant — most common primary malignant bone tumor - Who: Bimodal — teenagers (10–20 yrs, associated with rapid growth) and elderly (associated with Paget's disease) - Where: Metaphysis of long bones — distal femur, proximal tibia, proximal humerus. Knee region is most common overall - Histology: Malignant osteoblasts producing osteoid/woven bone directly - Clinical: Pain, swelling, tender mass. Can fracture pathologically - X-ray: - Codman's triangle — periosteal elevation at tumor margins - Sunburst pattern — spiculated new bone radiating outward - Prognosis: Poor without treatment; responds to chemo + surgery --- CARTILAGE-FORMING TUMORS 5. Chondroma (Enchondroma) - Nature: Benign - Who: Adults 20–50 - Where: Medulla of small bones of hands and feet (enchondroma = inside bone). Can also occur on surface (periosteal chondroma) - Histology: Lobules of hyaline cartilage, cytologically bland - Clinical: Usually asymptomatic; may cause pathological fracture - Special: Multiple enchondromas → Ollier disease . Ollier + soft tissue hemangiomas → Maffucci syndrome - X-ray: Lytic lesion with stippled/popcorn calcification --- 6. Osteochondroma - Nature: Benign — most common benign bone tumor overall - Who: Children and adolescents - Where: Metaphysis of long bones — distal femur, proximal tibia, proximal humerus - Structure: Bony projection (exostosis) with a cartilage cap on top — it's like the bone grew a mushroom-shaped outgrowth - Clinical: Usually asymptomatic; palpable hard lump. Stops growing when the growth plate closes - Risk: Cartilage cap 2 cm in adults → suspect malignant transformation to chondrosarcoma - Multiple osteochondromas → Hereditary Multiple Exostoses (HME) --- 7. Chondroblastoma - Nature: Benign but locally aggressive - Who: Young patients with open growth plates — adolescents - Where: Epiphysis of long bones — this is its defining location. Distal femur, proximal tibia, proximal humerus - Histology: Chondroblasts with "chicken-wire" calcification pattern - Clinical: Joint pain, swelling — because it's in the epiphysis, near the joint - X-ray: Well-defined lytic epiphyseal lesion --- 8. Chondrosarcoma - Nature: Malignant - Who: Adults 40, males females - Where: Central skeleton — pelvis, ribs, proximal femur, proximal humerus. Unlike osteosarcoma which loves the knee - Histology: Malignant cartilaginous cells, disorganized - Clinical: Slowly progressive deep pain and swelling - X-ray: Lytic lesion with rings-and-arcs calcification (characteristic) - Key point: Resistant to chemo and radiotherapy — surgery is the mainstay - Can arise from malignant transformation of osteochondroma or enchondroma --- MISCELLANEOUS TUMORS 9. Ewing's Sarcoma - Nature: Malignant — second most common malignant bone tumor in children - Who: Children and adolescents, 5–20 years. Rare in Black Africans - Where: Diaphysis of long bones — femur most common. Also flat bones (pelvis, ribs, scapula) - Histology: Small round blue cells — sheets of uniform small cells. Looks similar to lymphoma, neuroblastoma - Genetics: t(11;22) translocation — EWS-FLI1 fusion gene - Clinical: Pain, swelling, fever, raised ESR — can mimic osteomyelitis - X-ray: "Onion skin" periosteal reaction — layers of periosteal new bone - Treatment: Chemo + radiotherapy + surgery. More radiosensitive than osteosarcoma --- 10. Giant Cell Tumor (GCT) / Osteoclastoma - Nature: Locally aggressive — technically benign but behaves aggressively; can rarely metastasize - Who: Adults 20–40, after growth plates close . Females slightly males - Where: Epiphysis extending into metaphysis of long bones — distal femur, proximal tibia, distal radius. Always involves the epiphysis and extends to the articular surface - Histology: Multinucleated giant cells (osteoclast-like) scattered in a background of mononuclear stromal cells - Clinical: Pain and swelling near a joint - X-ray: "Soap bubble" appearance — lytic, expansile lesion with a thin shell of bone, no matrix calcification - Treatment: Curettage, but high recurrence rate --- QUICK COMPARISON TABLE Tumor Age Location X-ray Sign Key Fact --- --- --- --- --- Osteoma Adult Skull/sinuses Dense opacity Gardner syndrome Osteoid osteoma 10–25 Long bone cortex Nidus + sclerosis Night pain, relieved by aspirin Osteoblastoma Young adult Vertebral posterior Expansile lytic Pain NOT relieved by aspirin, 2cm nidus Osteosarcoma 10–20 / elderly Metaphysis (knee) Sunburst + Codman's Most common primary malignant Chondroma 20–50 Small bones hands/feet Popcorn calcification Ollier / Maffucci Osteochondroma Child/adolescent Metaphysis long bones Exostosis with cap Most common benign overall Chondroblastoma Adolescent Epiphysis Chicken-wire calcification Open growth plates Chondrosarcoma 40 Pelvis/central Rings and arcs Chemo-resistant Ewing's sarcoma 5–20 Diaphysis Onion skin t(11;22), small blue cells GCT 20–40 Epiphysis (post-growth plate) Soap bubble After plates close; osteoclast-like cells ---