Bronchial carcinoid with S-100 positive sustentacular cells.

A case of double bronchial typical carcinoid of the central type, with a nodal metastasis and paraneoplastic Cushing syndrome is reported. The case is remarkable because both the primary tumors and nodal metastasis were composed of a double cell population: one was arranged in nests, was argyrophilic, immunostained with PHE-5 monoclonal antibody, and contained neurosecretory granules; the other one was neither argyrophilic nor PHE-5-immunoreactive, but was strongly immunoreactive for S-100 protein, had a stellate morphology and was at the periphery of the nests of the other cells. The S-100 immunoreactive cells were regarded as a sort of "sustentacular" or "satellite" cells, which are themselves neoplastic. Bronchial carcinoids with S-100 positive cells, although strictly related with other bronchial carcinoids, may in fact represent a group of tumors with different histogenesis and/or differentiative pattern. More work should be done to elucidate whether there is any relevant clinical difference between bronchial carcinoids with or without S-100 reactive cells.