Microscopic examination showed a dermal neoplastic infiltrate composed of sheets of small, round cells, arranged in a rosettelike fashion, compressing the epidermis. The individual cells contained scant cytoplasm and powdery chromatin, suggesting a carcinoma of neuroendocrine origin. Numerous mitotic figures were identified. Immunohistochemical stains of the tumor were positive for cytokeratin 20, synaptophysin, and chromogranin and negative for leukocyte common antigen, cytokeratin 7, and S100 protein.
Erythematous Nodule on a Woman's Face. Arch Dermatol. 2001;137(10):1367-1372. doi: