Malignant mesothelioma of the peritoneum as the cause of a paraneoplastic syndrome: detection by 18F-FDG PET

Risk factors and prognosis of malignant peritoneal mesothelioma with paraneoplastic syndrome

BACKGROUND

Malignant peritoneal mesothelioma (MPM) is a rare and highly aggressive tumor. Its clinical manifestations are diverse, and the symptoms are not specific. Some patients will develop paraneoplastic syndrome (PS) during the disease course. This study aims to analyze the risk factors of PS in patients with MPM and their impacts on prognosis.

METHODS

The clinical data of MPM patients who underwent cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (CRS + HIPEC) at our center from June 2015 to May 2023 were retrospectively analyzed. MPM patients were divided into PS group and non-PS group according to the diagnostic criteria. Univariate and multivariate analyses were performed to explore the risk factors of PS in MPM patients, and to analyze the impact of PS on prognosis.

RESULTS

There were 146 MPM patients in this study, including 60 patients (41.1%) with PS and 86 patients (58.9%) without PS. The highest incidence of PS was thrombocytosis (33.6%), followed by neoplastic fever (9.6%). Univariate analysis revealed 8 factors (P < 0.05) with statistically significant differences between the two groups: prior surgical scores, targeted therapy history, Karnofsky performance status score, preoperative carbohydrate antigen (CA) 125 level, vascular tumor embolus, peritoneal cancer index, completeness of cytoreduction (CC) score and intraoperative ascites. Multivariate analysis identified 3 independent factors associated with PS: preoperative CA 125 level, vascular tumor embolus, and CC score. Survival analysis demonstrated that MPM patients with PS had worse prognosis, although PS was not an independent prognostic factor.

CONCLUSIONS

PS is not rare in patients with MPM, and is independently associated with preoperative CA 125 level, vascular tumor embolus and CC score. PS often indicates advanced disease and poor prognosis.

Peritoneal Mesothelioma-An Update

A remarkable amount of new information has been generated on peritoneal mesothelioma (PeM), ranging from nomenclature changes, including the removal of "malignant" when referring to this neoplasm and the use of the term "tumor" rather than "mesothelioma" to designate the neoplasm formerly known as "well-differentiated papillary mesothelioma", to the acknowledgment that PeMs can be associated with tumor predisposition syndromes or germline mutations. Although the disease is still more frequently seen in caucasian males, PeM is not uncommon in women. In addition, it can represent a diagnostic challenge when it has an uncommon presentation (ie, paraneoplastic syndrome or incidental finding) or when it has confounding histologic features. Ancillary testing, including immunohistochemical stains, in situ hybridization for CDKN2A or NF2 , and molecular studies, in selected cases, allows its correct diagnosis. The molecular landscape of PeM is still a work in progress; however, some findings, such as ALK gene rearrangements and EWSR1/FUS-ATF1 fusions, are specifically seen in PeM of young patients. The biological behavior of PeM is variable; however, cytoreductive surgery and hyperthermic intraperitoneal chemotherapy have markedly improved the survival of patients affected by this disease.

18F-FDG PET/CT in a recurrent diffuse malignant peritoneal mesothelioma

Peritoneal mesothelioma is a rare and aggressive tumor. Early diagnosis of the disease is difficult, delaying effective treatment. We report a case of recurrent, biphasic, diffuse, malignant peritoneal mesothelioma. Initial abdominal computed tomography showed abnormal but nonspecific findings suggestive of an ovarian malignancy, with a negative endoscopy and laboratory studies. An abdominal exploratory laparotomy found widespread malignancy within the peritoneum with a pathological diagnosis of peritoneal mesothelioma. A PET/CT imaging showed diffusely increased metabolic activity throughout the peritoneum, with no evidence of thoracic or pleural involvement. This case demonstrates the PET/CT findings seen with malignant recurrent peritoneal mesothelioma.

Imaging in the investigation of paraneoplastic syndromes

Paraneoplastic syndromes are a heterogeneous group of disease presentations caused by underlying tumours. As they are non-metastatic in nature an intensive diagnostic evaluation is warranted to identify potentially curable lesions. The selection of the appropriate method of imaging is important in these cases, especially when history and physical examination are unrevealing. In this review the important paraneoplastic syndromes and underlying malignancies are discussed along with relevant imaging strategies.