IMMUNOHISTOCHEMICAL ANALYSIS OF P53 MUTATIONS IN BRONCHIOLOALVEOLAR CARCINOMA AND CONVENTIONAL PULMONARY ADENOCARCINOMA

Mutations of p53 tumor suppressor gene have been shown to contribute t o tumorigenesis in a variety of human cancers. Normally, p53 protein d egrades rapidly and is not detected by immunohistochemical procedure, but mutant p53 and wild-type p53 stabilized by certain viral oncoprote ins can accumulate to immuno-histochemically demonstrable levels. Conv entional pulmonary adenocarcinomas and bronchioalveolar carcinomas, al though morphologically similar, exhibit different biological behavior and clinical prognosis. To explore the differences in the expression o f p53 protein in these two tumor types, we performed immunohistochemis try on 10 conventional pulmonary adenocarcinomas and 12 bronchioalveol ar carcinomas on formalin-fixed and paraffin-embedded material, using the commercially available monoclonal antibody against the mutant p53 protein. Intense nuclear staining was observed in 80% (8/10) of conven tional pulmonary adenocarcinomas, whereas all 12 bronchioalveolar carc inomas were negative for p53 protein. These observations indicate that altered p53 protein (probably mutant) is overexpressed in conventiona l adenocarcinomas and may be involved in its tumorigenesis or progress ion. On the other hand, the lack of p53 expression in bronchioalveolar carcinomas suggests that an alternative pathway is likely to be respo nsible for its tumorigenesis. Furthermore, p53 protein immunostaining may be useful as an adjunct in differentiating conventional pulmonary adenocarcinomas from bronchioalveolar carcinomas.