Giant cell carcinoma of the lung. A light and electron microscopic study.

Three cases of giant cell carcinoma of lung and six other lung carcinomas with large atypical cell formation were studied by both light and electron microscopy. The giant cell carcinomas showed unique light and electron microscopic features, whereas large atypical cells from other lung carcinomas usually retained some ultrastructural characteristics of their cellular origin. The giant cell carcinoma is characterized by abundant mitochondria, a concentric whorl of tonofilament-like fibrils, and aggregates of several pairs of centrioles. The "phagocytic activity" of the giant cell carcinoma is more likely attributable to the so-called tumor cell-tumor cell or leukocyte-tumor cell emperipolesis. Giant cell carcinoma of lung may originate from a primitive multipotential cell in the distal bronchiole or be associated with a squamous, glandular, or clear cell pattern. Whether in pure or mixed form, this tumor should still be considered a specific entity because of its unique light and electron microscopic features and the fulminant clinical course it follows despite rate reported exceptions.