Intracytoplasmic fibrillary inclusions in bronchial carcinoid.

A case of bronchial carcinoid with filamentous aggregates is described. The cytoplasmic inclusions were clearly demonstrated by means of Masson's trichrome stain in Bouin's fixed tissue, and the neoplastic cells showed a spontaneous green fluorescence with ultraviolet light. Electron microscopic examination showed that the inclusion bodies were composed of aggregates of filaments measuring 10A. They were located in the juxtanuclear region in close relation with mitochondria and the cisternae of the Golgi system. There were many neurosecretory granules inside the aggregates of filaments, some showing alterations in the dense core. From this data, we concluded that the aggregates seemed to represent an active rather than an involutional phenomenon and that their relation with hypoxemia and humoral influences needs further study.