Neuroendocrine differentiation in basal cell carcinomas.

Ten consecutive cases of basal cell carcinomas were reviewed. Nine of these displayed the typical histology of basal cell carcinoma, the other case was composed of small spindle to ovoid cells with scant cytoplasm and a high mitotic rate, resembling an "oat cell" carcinoma. These were studied using the immunoperoxidase technique for tissue localization of calcitonin, insulin, glucagon, somatostatin, ACTH, gastrin and nerve growth factor. Three cases were negative for all hormones tested. Three cases were focally positive for a single hormone; one each for calcitonin, somatostatin, and ACTH. Two cases were focally positive for ACTH and somatostatin and two cases were focally positive for calcitonin, somatostatin and ACTH. None of the other hormones displayed activity. The positive staining was eliminated after absorption by the specific antigen. This immunohistochemical study illustrated neuroendocrine differentiation in basal cell carcinomas as has previously been suggested by the Grimelius stain and electron microscopy. Thus, as demonstrated in other epithelial neoplasms, basal cell carcinoma may also display neuroendocrine differentiation. This illustrates the potential multidirectional differentiation in neoplastic epithelial cells.