Peripheral spindle-cell carcinoid tumor of the lung with type II pneumocyte features. An ultrastructural study with comments on possible histogenesis.

A peripheral spindle-cell carcinoid tumor of the lung was studied with the electron microscope. Tumor cells contained dense-core, neurosecretory granules, indicative of their carcinoid identity, and lamellar bodies indistinguishable from those of type II pneumocytes. This observation supports the concept that lung tumors with different histologic and growth patterns may have a common histogenetic basis.