Histopathology of cutaneous squamous cell carcinoma and its variants.

Squamous cell carcinoma is the second most common type of skin cancer, causing approximately 2,500 deaths in the United States each year. The principle risk factor for its development is ultraviolet light exposure. Conventional clinical and pathologic attributes of this neoplasm include an ulcerating papule located in a sun-exposed site with histologic sections showing an infiltrating neoplasm comprised of keratinizing epithelioid cells. Several histologic variants of squamous cell carcinoma with distinctive clinical and pathologic attributes including Bowen's disease, keratoacanthoma, acantholytic, spindle cell, desmoplastic, and verrucous and pigmented types have been described and are the topic of discussion in this article.