Acantholytic variant of squamous-cell carcinoma of the breast.

Three cases of acantholytic squamous-cell carcinoma of the breast are reported. They all had histological features resembling those of angiosarcoma or adenocarcinoma. They were not angiosarcoma, since in all three cases areas of squamous differentiation were present; in addition, the neoplastic cells were negative when stained for factor VIII, but were positive with anti-epidermal keratin. The glandular pattern exhibited, especially in Case 2, was difficult to differentiate from that of an ordinary carcinoma. However, the presence of dyskeratotic cells within the lumina, and the absence of alcian blue/periodic acid-Schiff positive material, and epithelial membrane antigen staining, were evidence against the diagnosis of adenocarcinoma. The patients died 5, 6, and 16 months after the diagnosis. Tumors with these histological features may have a very aggressive clinical course.