Although there are several types of non-melanoma skin cancer (NMSC), the most common types are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). These skin cancers account for 90% of all cases of skin cancer. Other NMSC’s include cutaneous lymphomas, merkel cell carcinoma, and Kaposi sarcoma. Approximately 20% of all Americans, an estimated 67,720 people in 2008, will develop NMSC during their lifetime.

Basal cell carcinomas develop from cells in the deepest layer (basal layer) of the superficial skin (epidermis) called basal cells. These cells help to replenish the skin by continually dividing to produce cells called keratinocytes. The keratinocytes are the cells that make up the majority of the epidermis. Squamous cell carcinomas develop from keratinocytes.

Several other skin lesions may be confused with NMSC or may develop into NMSC including seborrheic keratoses, actinic keratoses (which are precancerous lesions), cutaneous horns, and sebaceous gland hyperplasia. Therefore, any skin lesions which are new or changing should be evaluated by a physician.