Basal cell carcinomas are among the most common cutaneous malignant tumors. Two thirds of basal cell carcinomas are associated with actinic damage; however, one third occur in areas not exposed to the sun. These lesions, although histologically malignant, only rarely metastasize. However, if neglected, they are destructive and can cause disability or death by invading adjacent soft tissue, cartilage, or bone.

A basal cell carcinoma usually presents as a dome-shaped, white to pink papule or nodule with a raised pearly border and prominent superficial vessels. There may be scaling, crusting, or ulceration. Various other clinical types of basal cell carcinoma have also been observed. The cystic variety is translucent and contains gelatinous fluid. The sclerosing variety, appearing as a fibrotic, whitish, macular plaque with indistinct borders, may easily be overlooked. Superficial multicentric lesions may resemble asymptomatic eczematous plaques, although close inspection reveals a fine, raised pearly border. The pigmented variety may be confused clinically with a malignant melanoma. A rodent ulcer is usually a painless basal cell carcinoma that has progressively enlarged, producing tissue destruction with invasion and ulceration of underlying structures.

Multiple basal cell carcinomas, ranging in number from a few to hundreds, may occur in patients with the basal cell nevus syndrome, an autosomal dominant condition. The basal cell carcinomas begin to appear after puberty on the face, the trunk, and the extremities. Many are highly invasive and involve the embryonic cleft areas of the face, especially the regions around the eyes and the nose. Other associated features of the basal cell nevus syndrome include odontogenic jaw cysts, palmar and plantar pits, ectopic calcification (particularly of the falx cerebri), and ocular and skeletal abnormalities such as hypertelorism and shortening of the fourth and fifth metacarpals. This disease complex has also been termed Gorlin’s syndrome.