The cellular structure of bronchial carcinoids.

A histological and electronmicroscopic study of bronchial carcinoids indicated that these tumours are argyrophilic in keeping with their occurrence in tissue of embryologically foregut origin. Normal bronchi contain cells that resemble, in their electronmicroscopic content, intestinal Kultschitzky-type cells. Characteristic of the carcinoid cell is the presence of intracellular neurosecretory granules seen on electronmicroscopy despite the apparent absence of argentaffin granules under light microscopy.