Fine structure of bronchiolo-alveolar cell carcinoma

An electron microscopic study was made of 11 cases of bronchiolo-alveolar carcinoma and the findings compared with normal lungs and with biopsies from patients with diffuse lung disease. Six of the tumors displayed bronchiolar differentiation manifested by mucin secretion, secretory granules resembling those of non-ciliated bronchiolar cells, or by evidence of formation of ciliary basal bodies. Five other cases had atypical polymorphous cytoplasmic granules of uncertain composition. Such granules could indicate a relationship to either bronchiolar cells or to the hyperplastic alveolar epithelium common in damaged lung. Nuclear inclusions composed of membrane-bounded vacuoles and tubules were seen in some carcinomas, in granular pneumocytes in the neighborhood of carcinomas, and in a small proportion of cases of diffuse lung disease without tumors. They are believed to form as invaginations of the inner leaflet of the nuclear membrane and may be a degenerative phenomenon.