Melanocytic bronchial carcinoid tumor.

A melanin- and serotonin-producing bronchial carcinoid tumor is described. Melanin synthesis by neoplastic cells also containing electron-dense core (neurosecretory granules was documented by electron microscopy and serotonin content was found by biochemical assay to be 201.2 micrograms/g wet weight of tissue. Simultaneous demonstration of "endocrine" properties with characteristics of a cell of neural-crest origin provides strongly confirmatory evidence for the APUD cell theory of Pearse and makes an interesting commentary in regard to general theories of neoplasia.