Coalescent pleural malignant mesothelioma and adenocarcinoma of the lung, involving only minor asbestos exposure

Abstract

Coexistence of pulmonary adenocarcinoma and pleural malignant mesothelioma is extremely rare, although both are asbestos-related. Herein is presented a rare case of coalescent lung tumor made up of a malignant mesothelioma and a pulmonary adenocarcinoma in a 62-year-old Japanese man, a high-school teacher with only minor asbestos exposure. Preoperative diagnosis of adenocarcinoma was made on transbronchial biopsy. At surgery, multiple small white nodules were observed on the parietal pleural surface, opposite to the lung tumor. They were confirmed to be malignant mesothelioma on histopathology of paraffin section. The pulmonary tumor mass itself consisted of two distinct portions. The major part contained papillary proliferation of hobnail and columnar cells. Peripherally, neoplastic cells grew in a lepidic fashion and micropapillary growth was also detected. The other component featured tubular structures. The former was positive for adenocarcinoma markers such as CEA, Ber-EP4, PE-10, thyroid transcription factor-1 and Napsin A, and negative for mesothelial markers including calretinin, D2-40, WT-1 and HBME, while the latter was the opposite, resulting in a diagnosis of coalescing malignant mesothelioma and adenocarcinoma. The panel of antibodies used for immunohistochemistry was useful to distinguish the two different components in the one tumor.