<B>Osteochondroma </B>

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Osteochondroma

Etiology:
Unknown.

Pathogenesis:

• Believed to be the result of displaced fragments of the growth plate causing a displaced epiphysis to grow in an anomalous position.

Epidemiology:

• Three times more common in males than females.

General Gross Description:

• Also known as an exostosis.
• Benign lesion composed of a stalk and a rounded bony lesion, capped by cartilage.
• Most freqently seen near the ends of long bones.
• Irregularly mushroom shaped lesions, from 1-20 centimeters in size.

General Microscopic Description:

• External surface is made of cartilage.
• Inner portion composed of bone, often with a marrow cavity.
• Both the bone and the cartilage are histologically benign.

Clinical Correlations:

• Common lesion(s).
• Can occur as a solitary lesion or as one of multiple lesions.
• Individuals with multiple hereditary exostosis, an autosomal dominant hereditary disease, can have several hundred of these lesions.
• Present as slow growing masses which can be painful.
• Usually discovered in young adulthood.
• Usually stop growing when the patient reaches adult height.
• In patients with multiple hereditary exostosis, these lesions can be detected at childhood.
• Almost always benign; however, in patients with hereditary multiple exostosis, one or more of these lesions can undergo sarcomatous degeneration.

References:
•Robbins "Pathologic Basis of Disease" (Cotran, Kumar and Robbins, Eds.) 5th Edition. pp.1237