Ultrastructure of anaplastic bronchial carcinomas

Study of the ultrastructure of 6 anaplastic bronchial carcinomas has shown that this group of tumors is homogeneous. The fundamental cellular element is identical to that of the poorly differentiated squamous cell carcinoma. The progressive dedifferential of this fundamental cell results in the so-called “oat cell,” which is the end point of a process that may stop at any intermediate stage (round cell, fusiform cell, etc.). The maturation of the fundamental cell ends with its keratinization. Some tumor cells contain carcinoid-like granules, 1300 to 2000 Å in diameter, with a mean of 1400 Å. Their true nature requires further investigation.