Syringofibrocarcinoma versus squamous cell carcinoma involving syringofibroadenoma: is there a malignant counterpart of Mascaro's syringofibroadenoma?

Although a benign syringofibroadenoma has been recognized as an eccrine tumor exhibiting net-like ductal proliferation embedded in fibroma-like stroma, a malignant counterpart has not been described heretofore. An 82-year-old man with severely sun-damaged skin had a 3 cm plaque in the dorsum of his left hand. The clinical diagnosis was squamous cell carcinoma. Histologically, the lesion was a bowenoid squamous cell carcinoma, both in situ (Bowen's disease-like) and bluntly invasive, with a concurrent phase showing unequivocal and widespread ductal differentiation, local expression of carcinoembryonic antigen, and sclerotic stroma. This syringofibrocarcinoma also impinged laterally on a mature and benign syringofibroadenoma and occurred above a minute deep dermal trichoepithelioma. This report presents a probably unrecognized new malignant tumor, clearly distinct yet related to both squamous cell carcinoma and eccrine carcinoma. Because its organoid architecture and the resemblance to and impingement on syringofibroadenoma, the term syringofibrocarcinoma is proposed.