Type II pneumocytes in pulmonary tumors. Implications for histogenesis.

Bronchioloalveolar carcinomas (n = 45), intravascular bronchiolo-alveolar tumors (n = 8), and sclerosing hemangiomas of the lung (n = 2) were stained for surfactant apoprotein by the immunoperoxidase method. Of the bronchiolo-alveolar carcinomas, 12 were found to be carcinomas of type II pneumocytes and the remaining 33 tumors were designated as nontype II pneumocytic bronchiolo-alveolar carcinomas. Twenty-five of these tumors displayed trapped benign type II pneumocytes within the tumor masses. In the case of intravascular bronchioloalveolar tumors, none of the tumors demonstrated staining of tumor cells for surfactant apoprotein. In the two cases of sclerosing hemangiomas, the type II pneumocytes were exuberant and numerous, and in one case contained intranuclear inclusions of surfactant apoprotein. This article discusses the implication of the presence of benign type II pneumocytes in pulmonary tumors.