Osteochondroma

General: Sometimes called merely exostosis, which strictly speaking is a more generic term for any outgrowth of bone. Often asymptomatic. More common in young (20's) males and the metaphyses around the knee. May occur as a sporadic solitary lesion or as multiple lesions associated with autosomal dominant hereditary multiple exostoses or a contiguous gene-deletion syndrome — Langer-Giedion syndrome or Potocki-Shaffer syndrome.

Gross: Benign outgrowth of cortical and medullary bone, with a cartilaginous cap. May be sessile or pedunculated.

Imaging:

Microscopic: The external surface is covered by a thin pink periosteal membrane. The cartilage cap consists of clusters of chondrocytes & lacunae with abundant chondroid matrix. Towards the base the chondrocytes arrange into normal columns overlying cancellous bone, possibly containing islands of cartilage. Excess cartilage with no bone on the slide should raise the suspicion of chondrosarcoma.

Differential Diagnosis:

Stains:

• Positive:
• Negative:
• Suggested, focused panel:

((())) AFIP Bones & Joints 2005

Images:


Cases:

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