A giant mass on the left shin: report of a case.

A woman presented to our department with an asymptomatic progressive peripherally expanding skin lesion on her left shin for 6 years. The doctor in a local clinic considered it was a deep fungal infection, however, treatment with itraconazole systemically was ineffective. A second biopsy showed papillomatous hyperplasia and a central keratin-filled crater with a buttress like extension of surrounding epidermis and a well-demarcated regular base. In the upper dermis, diffused infiltration of mixed inflammatory cells was observed with perivascular infiltrate. Deeper dermis, appendageal structures and subcutaneous tissue were unremarkable. Periodic acid-schiffic staining and diamine silver staining of the specimen were negative. A diagnosis of Keratoacanthoma centrifugum marginatum (KCM) was finally established.