Osteochondroma Pathology Case no 35.pptx

Osteochondroma

1. Case no: 35 35 yr Male, Complains of knee swelling

2. Scanner view: A well-circumscribed lesion with an outer zone of hyaline cartilage cap and underlying bone trabeculae with marrow spaces. Cartilage cap is arranged in lobules resembling an epiphyseal growth plate.

3. Low power : The cartilage cap is composed of lobules of hyaline cartilage. Chondrocytes are arranged in clusters within lacunae. Beneath the cartilage cap, there is endochondral ossification forming bony trabeculae.

4. Low power

5. High power : Chondrocytes within the cartilage cap show uniform round to oval nuclei, located in lacunae. They may appear in clusters but show no nuclear atypia, no binucleation, and no mitoses. The matrix is hyaline with evidence of calcification in areas.

6. Impression : Features are consistent with Osteochondroma

7. Review of literature A benign cartilage-capped bony projection (exostosis) that arises on the external surface of bone, usually near the growth plate (metaphysis). Composed of bone (continuous with cortex & medullary cavity) and a cartilage cap. Common Sites - Long bones near metaphysis:Distal femur, proximal tibia, proximal humerus

8. Etiology & Pathogenesis Developmental defect, not a true neoplasm (arises from displaced growth plate cartilage). Associated with EXT1, EXT2 mutations in hereditary multiple osteochondromas. Usually occurs during childhood/adolescence, grows until skeletal maturity, then stops.

9. Diagnostic Criteria: Cartilage can with growth plate like architecture Stalk continuous with cortex and marrow of parent bone. Can < 2 cm in adults.

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