Rarely occuring and newly described histological variants of cutaneous squamous cell carcinoma. Classification based on histopathology, cytomorphology and biologic behavior

The histological spectrum of squamous cell carcinoma (SCC) of the skin is p resented, including recently mentioned and rarely ap pea ri ng tumor subtyp es. Beside the most frequently occuring common SCC with variable degree of differentiation, the following tumor forms can be identified microscopicall y: Bowen-SCC, acantholytic SCC, clear cell SCC, spindle cell SCC, keratoaca nthoma-like SCC, desmoplastic SCC, neurotrophic SCC, verrucous SCC, adenosq uamous carcinoma and basosquamous cell carcinoma. The classification of lym phoepithelioma-like carcinoma as a cutaneous SCC Variant is disputed, becau se epidermal connections are regularly absent and evidence of glandular and follicular differentiation suggest an adnexal origin. Beside the descripti on of distinctive histological and cytomorphological features of each SCC s ubtype, important differences in malignant behavior and clinical course are emphasized.