A carcinoma with features of porocarcinoma, dermal ductular carcinoma, and squamous cell carcinoma in situ.

We report the case of a 69-year-old Japanese woman with an extraordinary carcinoma on her back. The tumor had three different histologic components including porocarcinoma, dermal ductular carcinoma, and an area resembling squamous cell carcinoma in situ (SCCIS). Sweat gland tumors (SGTs) are known to have a wide spectrum of pathologic appearances and variable grades of differentiation. This report expands the spectrum of reported combinations.