Localized malignant pleural sarcomatoid mesothelioma misdiagnosed as benign localized fibrous tumor

Abstract

Localized malignant pleural mesothelioma (LMPM) is a rare tumor with good prognosis by surgical resection. We report an atypical case of malignant pleural sarcomatoid mesothelioma (SM) in an asymptomatic 65-year-old woman, who had no history of exposure to asbestos. She presented with a small pleural mass without pleural effusion and was misdiagnosed as a benign localized fibrous tumor (BLFT) on pathologic examination through a surgical tumor specimen. However, seven months later, the patient returned with serious cancerous symptoms. A large recurrent tumor mass was found within the chest wall invading at the old surgical resection site. SM, a subtype of LMPM, was confirmed with histopathogy and immunohistochemisty. In conclusion, malignant pleural mesothelioma (MPM) can present with typical radiologic finding similar to a BLFT, and has a wide histopathologic presentation in biopsy specimen. A thorough pathologic investigation should be attempted even when a pleural mass resembles benign, localized, and small on radiologic studies.

Keywords: Pleura; computed tomography (CT); lobectomy; mesothelioma; pathology.

Figure 1

Initial chest X-ray and CT scan. (A) Chest X-ray shows a well-defined mass abutting the left lateral chest wall; (B,C) contrast-enhanced CT scan show a solitary sharp homogeneous oval enhancing mass abutting the pleura with diameter of 3.5 cm on the left lateral chest wall. The mass is pedunculated in the upper part of the left chest wall (B). Pleural effusion is not observed.

Figure 2

Follow-up chest X-ray and CT scan obtained seven months after surgical resection of pleural mass. (A) Chest X-ray shows a large recurrent mass at the site of previous mass excision; (B) contrast-enhanced CT scan shows a solitary large well-defined homogeneous enhancing mass in the left lower hemithorax. There are sign of bony destruction of adjacent rib (arrowheads) and chest wall invasion (white arrow). Image noise in the mass was owing to the low radiation dose CT scanning with iterative reconstruction algorithm. A 100 kVp and dose modulation of mAs was used.

Figure 3

Histopathologic examination of pleural mass. (A) The 12× magnification on a light microscopy shows pleural mass infiltrating into the parenchyma of the lung (arrowheads); (B) the 200× magnification on a light microscopy shows spindle cell proliferation with mild pleomorphism and frequent mitosis (black arrows) in the collagenous background; (C) the 100× magnification on a light microscopy shows D2-40, a novel mesothelial marker, indicates strong positive for malignant mesothelioma.