Bronchial carcinoids and phaeochromocytomas. A comparative study with special emphasis on S-100 protein, serotonin and neuron-specific enolase (NSE) immunoreactivity.

A comparative study of bronchial carcinoids (9 cases) and phaeochromocytomas (8 cases) were performed. Both types of tumour exhibited neuron-specific enolase (NSE) immunoreactivity and an argyrophil reaction, and displayed a few scattered argentaffin and serotonin immunoreactive tumour cells. In addition, four of the nine bronchial carcinoids and six of the eight phaeochromocytomas were S-100 protein immunoreactive. The stained cells were located mainly in the periphery of the tumour cell aggregates and possessed long cytoplasmic processes surrounding unreactive tumour cells. The similarity between the two tumour types, especially in their morphology and S-100 protein immunoreactivity, indicates that bronchial carcinoids, or at least some of them, are histogenetically closely related to phaeochromocytomas and might derive from the peripheral nervous system.