Origin of bronchioloalveolar carcinoma and peripheral bronchial adenocarcinoma

The morphologic distribution of newly synthesized glycoproteins in a bronchioloalveolar carcinoma and in a peripheral bronchial adenocarcinoma with areas of bronchioloalveolar differentiation was determined and compared with bronchiolar epithelium and type II alveolar cells. Tissues were maintained in vitro, and autoradiography was used to reveal locations of glycoproteins metabolically labelled with 3H-glucosamine. Both tumors displayed glycoprotein secretory activity as most incorporated radioactivity was rapidly released from cells. Silver grains were associated with cytoplasmic granules and mucinlike secretions in the bronchioloaveolar carcinoma and granules plus unidentified secretions in the bronchial adenocarcinoma. Clara cells exhibited an association of newly synthesized glycoproteins with cytoplasmic granules similar to those found in the tumors. In bronchiolar ciliated epithelium, as in bronchial ciliated cells and central bronchogenic adenocarcinomas, glycoproteins accumulated over apical cell surfaces and were not rapidly secreted. Type II cells incorporated label into secreted contents of cytosomal inclusions and unidentified cytoplasmic material. The observations suggest that a bronchioloalveolar carcinoma and a peripheral bronchogenic adenocarcinoma are distinct from common bronchogenic adenocarcinomas and are derived from secretory cells that resemble bronchiolar Clara cells.