Immunohistological analysis of surfactant-apoprotein in the bronchiolo-alveolar carcinoma.

Fifty-five cases of bronchiolo-alveolar carcinoma were examined immunohistochemically using mono-specific antisurfactant apoprotein IgG obtained from a rabbit immunized with monkey surfactant preparations. Formalin-fixed and paraffin-embedded lung tissues were stained by an immunoperoxidase method. Antibody stained the normal and hyperplastic alveolar type II pneumocytes, but did not stain bronchial epithelium or other lung cells. In tumor tissue, 26 (47.3%) of 55 cases were positively stained in the cytoplasm, and 15 showed reaction products in both the cytoplasm and intranuclear regions. By electron microscopy osmiophilic lamellar bodies and microvilli on the free surface, thought to be characteristic of type II pneumocytes, were seen in tumor cells (2 cases). In the five cases, the nuclei contained branching tubular inclusions. The results of this study support the idea that certain bronchiolo-alveolar carcinomas originate from type II pneumocytes, the intranuclear inclusions may represent an abnormal proliferation of nuclear membranes containing surfactant-apoprotein.