Histologic variants of squamous cell carcinoma of the skin.

Squamous cell carcinoma (SCC) is the second most common type of skin cancer, with basal cell carcinoma being the most common. However, some argue that an actinic keratosis should be considered as an SCC that is superficial.1 If so, then SCC could be considered the most common type of skin cancer. The tumor typically appears as a papule or nodule, with varying degrees of hyperkeratosis and ulceration that arises on the sun-exposed skin of elderly patients (Fig 1). The disease has been linked to immunosuppression, arsenic exposure, radiation, chronic ulceration, and human papillomavirus (HPV) infection.2 The histology reveals a proliferation of atypical keratinocytes that invade the dermis, with areas of detachment from the overlying epidermis. These anastomosing growths of cords and nests are composed of cells that have a glassy eosinophilic cytoplasm and enlarged nuclei. Mitotic figures, keratin pearls, and dyskeratotic keratinocytes are variably present. On higher power, intercellular bridges may be seen.