IMMUNOHISTOCHEMICAL ANALYSIS OF PANCREATIC SECRETORY TRYPSIN-INHIBITOR EXPRESSION IN PULMONARY ADENOCARCINOMA - ITS POSSIBLE PARTICIPATION IN SCAR FORMATION OF THE TUMOR-TISSUES

The expression of pancreatic secretory trypsin inhibitor (PSTI) was examined immunohistochemically in pulmonary adenocarcinoma. Of 86 carcinomas examined, 65 (76%) showed immunoreactivity for PSTI. Cases with the papillary subtype and those with early stage disease contained PSTI in cancer cells more frequently and were more strongly positive. There was a slight tendency to strong expression of PSTI in cases with the histologically well-differentiated type, tumor size of approximately 30 mm maximum diameter, and marked scar formation. Furthermore, 3 7 cases, which were the majority of the PSTI-positives, appeared to contain PSTI predominantly in cancer cells within the central or subpleural scar tissue and/or its surrounding tissue. Thus, pulmonary adenocarcinoma may commonly express PSTI and, considering previous reports that PSTI acts as a growth factor-like substance on fibroblasts in vitro in addition to the present findings of its immunohistochemical distribution in the tumor tissues, it is suggested that PSTI expressed in cancer cells of some pulmonary adenocarcinomas may possibly participate in tumor scar formation.