A 58-year-old man has had a discharging sinus over his chronically infected tibial shaft for 25 years. Recently the sinus margins have become everted, friable, and bleed on touch. Biopsy of the sinus edge will most likely show:

• A Basal cell carcinoma
• B Well differentiated squamous cell carcinoma ✓
• C Chronic granulation tissue with pseudomonas colonisation
• D Recurrent Brodie abscess lining

Explanation

B long standing sinus tract of chronic osteomyelitis carries a well recognised risk of malignant transformation, almost always squamous cell carcinoma arising from the metaplastic squamous epithelium lining the tract, typically after decades of drainage. Eversion, induration, bleeding, and foul discharge are warning signs demanding biopsy. Basal cell carcinoma does not arise in sinus tracts, and simple granulation tissue does not produce everted edges.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.