Contributor: Gordon K. Klintworth
Basal cell carcinoma (rodent ulcer, basal cell epithelioma, basalioma, Jacob ulcer) is a locally aggressive carcinoma of the skin that arises from the basal layer of the epidermis. It is the most common human cancer and the most frequent malignant tumor of the eyelid. In the United States ~750,000 basal cell carcinomas are detected each year. Basal cell carcinoma accounts for ~90% of all eyelid malignancies in the United States, where it is 16 times more common than sebaceous carcinoma, the second most common eyelid malignancy, and 18.5 times more common than squamous cell carcinoma [carcinoma - squamous cell]. This tumor most often affects the lower eyelid. Risk factors for basal cell carcinoma of the eyelid include chronic solar irradiation, xeroderma pigmentosum, and prior local radiotherapy, as in the treatment of malignant neoplasms of the paranasal sinus. Some cases are a manifestation of the basal cell nevus syndrome due to mutations in the PTCH1 gene. Others are related to mutations in the PTCH2 gene. Several variants of the tumor are recognized. They include the ulcerated basal cell carcinoma [basal cell carcinoma - cicatricial], clear cell basal cell carcinoma [basal cell carcinoma - clear cell], cystic basal cell carcinoma [basal cell carcinoma - cystic], field fire basal cell carcinoma [basal cell carcinoma - field fire], morphea-like basal cell carcinoma [basal cell carcinoma - morphea-like], multfocal focal basal cell carcinoma [basal cell carcinoma - multifocal], nevoid basal cell carcinoma [basal cell carcinoma - nevoid], nodular basal cell carcinoma [basal cell carcinoma - nodular], nodulo-ulcerative basal cell carcinoma [basal cell carcinoma - nodulo-ulcerative], pigmented basal cell carcinoma [basal cell carcinoma - pigmented], and ulcerated basal cell carcinoma [basal cell carcinoma - ulcerated]. The tumor often has elevated, pearly margins and an ulcerated center. A neglected basal cell carcinoma ("rodent ulcer") can destroy facial structures producing ghastly disfigurement. During the excision of a basal cell carcinoma the surgical margins of resection should be evaluated under frozen section control because this significantly reduces the incidence of tumor recurrence. Some benign tumors [pilomatrixoma] are sometimes mistaken for basal cell carcinoma