Melanocytic neuroendocrine carcinoma of the thymus

A neuroendocrine carcinoma of the thymus with an ectopic adrenocorticotropic hormone (ACTH) syndrome and melanocytic differentiation is described. ACTH, neuron-specific enolase (NSE) and S-100 protein were identified in the tumor by immunocytochemistry. Neurosecretory granules and melanosomes could be demonstrated in different cell populations by electronmicroscopy. The clinicopathologic findings are presented. The literature is briefly discussed.