Trichilemmal carcinoma with neuroendocrine differentiation

We report a 12-mm nodular, cream-coloured skin lesion that appeared on the left nasal ala in an 81-year-old man. This trabecular infiltrative tumour showed keratin microcysts, stromal hyalization, cytoarchitectural malignancy features, colonizing melanocytes, and immunoexpression of epithelial membrane antigen, cytokeratin 15/20, chromogranin, synaptophysin and CD56. To our knowledge, this is the first documented case of a trichilemmal carcinoma with neuroendocrine differentiation and melanocyte colonization, which is suggested by the trabecular growth pattern and requires immunohistochemical confirmation. The colonization of the epithelial nests by nonatypical dendritic or spindle melanocytes is a clue to morphological recognition of pilar neoplasms, along with the presence of stromal induction (CD34-positive peritumoral spindle cells), catagen-like apoptotic bodies, calcifications, keratin microcysts and cell balls.