Metastatic basal cell carcinoma. Report of five cases

Background. Metastatic basal cell carcinoma (MBCC) is rare. Risk factors for the development of MBCC include a history of persistent basal cell carcinoma (BCC) for many years, refractory to conventional methods of treatment and previous radiation treatment either in early adulthood or for localized cancer. Most MBCC originate from large tumors. Methods. The authors report five patients with basal cell carcinomas (BCC) of the ear (two patients), scalp, inner canthus, and nasolabial fold that metastasized to the regional lymph nodes, skin, and submandibular gland. In addition, the authors reviewed more than 40 reports of MBCC (n = 65) from 1981 to 1991 and tabulated the primary tumors by size and depth of invasion according to TNM classification, a classification that previously has not been used for BCC. Results. The authors tabulated the size distribution of tumors of 45 patients with MBCC. The overall mean and median diameters of the primary BCC were 8.7 and 7.0 cm, respectively. The mean area of the primary MBCC lesion that originated on the face and trunk was 62 and 217 cm2, respectively. Using the TNM classification, approximately 9% of MBCC originate from tumors smaller than 10 cm2. In addition, the authors found that large (T2 and T3) and deep (T4) BCC account for approximately 75% of the metastatic tumors. Metastatic BCC from primary tumors smaller than 1 cm in diameter are exceptionally rare. Conclusions. Approximately 67% of MBCC (n = 238) originate from facial sites. Using the data base of the Mohs Surgery Clinic, the authors found that BCC greater than 3 cm in diameter have approximately a 1.9% incidence of metastasis, and the overall rate of metastases for morpheaform BCC is less than 1%. Patients with tumors classified as T3 and T4 lesions ideally should be followed up for 10 or more years for the remote possibility of the development of MBCC.