A case of malignant peritoneal mesothelioma revealed with limitation of PET-CT in the diagnosis of thoracic metastasis

Abstract

A 47-year-old man was referred to our hospital because of a 2-month history of dry cough, 2-kg weight loss, and a feeling of abdominal fullness. The PET-CT scan depicts the intense standard uptake values (SUVs) of the anterior and subphrenic lymphnodes, and intraperitoneal cavity, especially in the omentum, while, no uptake was found in the pleural cavity. Based on the pathological findings of the open lung biopsy specimens, he was diagnosed with malignant peritoneal mesothelioma of epithelioid type with thoracic metastasis. The present case demonstrated the some of the limitations of PET-CT in the diagnosis of malignant mesothelioma, which failed to detect pleural involvement despite aggressive invasion by this tumor.

Keywords: Malignant peritoneal mesothelioma; fluorodeoxyglucose (FDG) positron emission tomography (PET) computed tomography; open lung biopsy; thoracic metastasis.

Figure 1

A. Chest radiograph taken on the first visit shows tiny nodules scattered throughout bilateral lung fields, a right pleural effusion, and bilateral hilar lymphadenopathy; B & C. Random distribution of multiple tiny nodules is seen in the lung parenchyma, as well as a moderate amount of right pleural effusion with bilateral hilar lymphadenopathy.

Figure 2

Chest CT taken on the first visit demonstrates cardiophrenic (A), and intraabdominal lymphadenopathy (B). The CT findings also show a small amount of ascites with smooth parietal peritoneal thickening (B, arrowhead), fine, nodular soft tissue (B, thin arrow), and a large mass-like lesion (B, thick arrow) within the greater omentum, predominantly in the left upper abdomen. PET-CT scan taken 3 weeks after his first visit to our department depicts the intense SUV of subphrenic lymphadenopathy (C), and intraperitoneal cavity (D), especially in the omentum. PET, positron emission tomography.

Figure 3

Intraoperative photograph showing scattered white-colored nodules both in the parietal (asterisk) and visceral pleura (double asterisk) in the right hemithorax.

Figure 4

A. On hematoxylin and eosin staining from the right lower lobe specimen, atypical cells can be seen to infiltrate within the visceral pleura and connect to the lung parenchyma in the myxoid background; B. On magnified image (400×), those atypical cuboidal cells form tubular and papillary structures.

Figure 5

On immunohistochemistry, the tumor cells are positive for calretinin (A), HBME-1 (B), WT-1 (C), and CK5/6 (D). HBME-1, Hector Battifora-mesothelin-1; WT-1, Wilm’s tumor-1; CK, cytokeratin.