Pleural malignant fibrous histiocytoma concomitant with pulmonary adenocarcinoma

A rare autopsy case, in which pleural malignant fibrous histiocytoma (MFH) and peripheral pulmonary adenocarcinoma were present concurrently in the right thorax, is described. Clinically, only a pleural mass was detected because of massive pleural effusion. Since cytologic examination of the effusion showed only adenocarcinoma cells, the pleural mass was considered to be enlarged mediastinal lymph nodes due to metastasis of adenocarcinoma. Histopathologically, the pleural mass showed the features of a common type of MFH, accompanied by metastatic adenocarcinoma cells in the pleural lymphatics. No mixture of MFH and adenocarcinoma cells was present. Immunohistochemically, the MFH lesion showed positive staining for alpha-1-antitrypsin, alpha-1-chymotrypsin, and factor XIIIa, but no reactivity for cytokeratins. The adenocarcinoma lesion showed positive staining for carcinoembryonic antigen (CEA), and contained hyaluronidase-resistant mucin. To our knowledge, this is the second reported case of pleural MFH with pulmonary adenocarcinoma.