Immunohistochemical study of basement membrane antigens in bronchioloalveolar carcinoma.

Bronchioloalveolar carcinoma (BAC), not yet completely defined as a biologic entity, has recently been classified into two different types. Immunohistochemical investigations, aimed at characterizing basement membrane (BM) behavior in the two types of BAC, revealed different distribution patterns. The first (Type I BAC) showed a linear staining for laminin and Type IV collagen similar to normal lung. Fibronectin was widely present in the septal interstitium and patchily distributed along the BM. The second (Type II BAC) showed a variable reaction for Type IV collagen and fibronectin, whereas laminin was absent or appeared as short, interrupted tracts around the epithelial neoplastic population, similar to conventional adenocarcinoma of the lung. These results suggest that only Type I BAC shows structural characteristics different from those of conventional adenocarcinoma of the lung.