Solitary Malignant Pleural Mesothelioma: A Rare Presentation

A 62-year-old female farmer presented with a 10-day history of cough and 1 week of left-sided chest pain and tightness.On chest computed tomography (CT), a wellcircumscribed, homogeneous soft tissue mass (40 mm 23 mm, 49 Hounsfield units [HU]) was observed adjacent to the left diaphragm, with mild contrast enhancement (83 HU) (Figure 1).Left pleural effusion was present, but no mediastinal lymphadenopathy or rib destruction was seen.The key feature on prone-position CT was positional mobility of the mass that suggested a pedunculated pleural origin.A solitary, smooth-surfaced tumor arising from the diaphragmatic pleura was visualized during medical thoracoscopy (Figure 2).The results of biopsy and immunohistochemistry (IHC) were as follows: Histologic examination detected malignant spindle and epithelioid cells with invasive growth.The IHC profile was positive for calretinin, Wilms' tumor 1 (WT-1), cytokeratin (CK)5/6, and CK7 (confirming mesothelial origin), and it was negative for thyroid transcription factor 1 (TTF-1) and P40 (excluding carcinoma).Ki-67 was at 20% (moderate proliferative activity).