Basal cell carcinoma is a common cutaneous neoplasm that rarely metastasizes. We studied the clinical and pathologic features of 17 patients with metastatic basal cell carcinoma as recorded in the files of the Armed Forces Institute of Pathology (AFIP). Sixteen of the patients were male, and as far as it could be determined, all were white. The most frequent site of metastasis was lung (9 cases), followed by bone (9, lymph nodes (4), liver (3), spleen (l) , and adrenal gland (1). Thirteen of the patients had metastatic lesions involving only one organ system. Mean survival time after metastasis was 1.6 years. Features of metatypical (basosquamous) basal cell carcinoma were common in the primary and recurrent tumors, and metastatic lesions generally had a metatypical or adenoid pattern. Two of the five bony metastases demonstrated shadow cells characteristic of pilomatrixoma. The metatypical pattern of a basal cell carcinoma is a feature of an aggressive lesion with the ability to metastasize. Cancer 46:748-757. 1980. N 1827, ARTHUR JACOB, an Irish surgeon, provided I the first clinical description of a basal cell carcinoma when he detailed findings of extensive rodent ulcers on the faces of 3 patients.14 Cecil Beadles 67 years later reported the first case of a metastatic rodent ulcer' in a 46-year-old man with a primary lesion on the face and metastases to a submandibular lymph node. Beadles provided for the first time a histologic description of the metastatic lesion. In 1900, Krompecher began publishing a series of papers on the detailed histologic features of basal cell carcinomas,lS which he believed were derived from the basal cells of the epidermis. Over the past three-quarters of a century, numerous case reports and reviews of the literature have been published on metastatic basal cell carcinomas. The questions generally asked have been as follows: 1. What is the incidence? 2. What are the demographic and clinical features of the patients? 3. the response to therapy? 4. What are the pathologic features? and 5. What are the conditions that allow or promote the occurrence of a metastatic lesion? We have studied 17 cases of metastatic basal cell carcinoma from the files of the AFIP. Our purpose was to find answers to all of the above except the question dealing with incidence. Since material submitted to AFIP is selected and not random, a true incidence could not be obtained. Recent reviews of the literature, however , have estimated the incidence to range from 0.028% to 0.55% depending upon the population These figures reinforce the general concept that metas-tasis from a basal cell carcinoma is a relatively rare event. Materials and Methods Twenty-five cases were available for study from the files of the AFIP, submitted from civilian and military sources. They were coded under the following categories: metastatic basal cell carcinoma (20 cases), metastatic adnexal carcinoma (2), basal cell carcinoma of bone and muscle (l), mixed carcinoma of lung (l), and unclassified carcinoma (1). Follow-up of each pati...