Case reports of primary pulmonary adenocarcinoma with pleural spread: So-called pseudomesotheliomatous adenocarcinoma

We report two autopsy cases of primary pulmonary adenocarcinoma associated with unusual pleural spread. Both patients had confirmed history of asbestos exposure. In the first patient the tumor was localized in one pulmonary lobe with marked infiltration into pleura, chest wall and diaphragm. In the second patient the entire right lung was covered by irregularly thickened tumor. Both tumors were mainly located in the extrapulmonary area and the intrapulmonary portions represented only minor components. Histologically, tumor cells demonstrated glandular and papillary growth patterns associated with focal hobnail-like features. Immunohistochemical evaluation revealed diffuse and marked immunoreactivity of TTF-1, CEA, CD15 and MOC31 in both cases, while calretinin, CK5/6, vimentin, thrombomodulin and HBME-1 were broadly positive in one case. D2-40 was not detected in either case. Examination using electron microscopy revealed the presence of sparse and short microvilli in tumor cells. All of the above findings are consistent with adenocarcinoma of the lung. Primary adenocarcinoma with a characteristic pleural extention grossly resembling malignant mesothelioma has been previously reported in the literature as pseudomesotheliomatous adenocarcinoma. This is the first report of pseudomesotheliomatous adenocarcinoma displaying variable immunoprofile with a diagnosis using electron microscopical examination. Additionally, we performed quantitative analysis of asbestos bodies in pseudomesotheliomatous adenocarcinoma.