Infiltrative basal cell carcinoma mimicking tinea corporis.

The diagnosis of infiltrative basal cell carcinoma (BCC) can be delayed owing to its often subtle clinical findings. A 90-year-old woman presented with an asymptomatic annular pink plaque on her left shin that was clinically diagnosed as tinea corporis. After years of not responding to topical anti-fungal therapy, biopsies confirmed a diagnosis of infiltrative BCC. We discuss the differential diagnosis of the case, the difficulties in identifying infiltrative BCC, and the pathologic features of infiltrative BCC.