Bone tumers

Osteoid Osteoma

Age: Young males

Location: Cortex of femur/tibia

Key Feature: Severe nocturnal pain relieved by NSAIDs

Microscopy: Woven bone trabeculae rimmed by osteoblasts

Gross: Small, red-tan nidus

Osteosarcoma

Age: Adolescents (<20)

Location: Metaphysis, especially around knee

Key Feature: Most common primary malignant bone tumor; painful enlarging mass

Microscopy: Malignant pleomorphic cells producing osteoid

Gross: Large, destructive, tan-white tumor with hemorrhage

Chondroma (Enchondroma)

Age: 20–50

Location: Small bones of hands/feet

Key Feature: Asymptomatic; incidental finding

Microscopy: Benign chondrocytes in hyaline cartilage

Gross: Small (<3 cm), gray-blue, translucent

Chondrosarcoma

Age: >40

Location: Axial skeleton (pelvis, shoulder, ribs)

Key Feature: Painful mass; second most common malignant bone tumor

Microscopy: Atypical cartilage cells; graded 1–3

Gross: Bulky, gray-white cartilage with necrosis

Giant Cell Tumor

Age: 30–50

Location: Epiphysis of long bones

Key Feature: Contains osteoclast-type giant cells; high recurrence

Microscopy: Numerous giant cells + mononuclear stromal cells

Gross: Soft, friable, brown-red lesion

Ewing Sarcoma

Age: Children & adolescents

Location: Long bones & pelvis

Key Feature: t(11;22) EWSR1 translocation; tender, warm swelling

Microscopy: Sheets of small round blue cells; ± Homer-Wright rosettes

Gross: Soft, tan-white tumor with hemorrhage & necrosis