A Case of Localized Malignant Peritoneal Mesothelioma With Lung Cancer Detected by 18F-FDG PET/CT

Localized Malignant Peritoneal Mesothelioma (LMPeM) in Women: A Clinicopathologic Study of 18 Cases

Localized malignant peritoneal mesothelioma is a rare tumor with limited information in the literature. In this study, we present our experience with 18 cases seen in our hospital over a period of 43 years (1978 to 2021). Patients' median age was 55 years (y) (range: 33 to 79 y) and most of them were Caucasians. Patients presented with abdominal pain (11), ascites and right leg swelling (1), abdominal mass (1), and as incidental finding (1). Thirty percent of patients reported asbestos exposure, and all patients with available information had family history of tumors; a third had personal history of tumors. Seventy-seven percent had some form of abdominopelvic surgery and/or inflammatory process. Most cases had microscopic features typically seen in malignant mesothelioma; however, some cases had confounding features such as signet-ring cells, spindle cells, clear cell changes, and adenomatoid tumor-like appearance. BAP-1 by immunohistochemistry was lost in 1/3 cases. Only 1 patient underwent genetic testing and had an MSH2 germline mutation. Homozygous deletion of CDKN2A by FISH was not found in 1 tested case, although next-generation sequencing identified a CDKN2A pathogenic mutation. 16/18 (88%) had surgical treatment, and some also received adjuvant chemotherapy. The mean overall survival (OS) of our patients was 80.4 months (95% confidence interval: 54.3-106.52); the 3-year OS was 79%, while the 5-year OS was 52.6%. Fifty-three percent of patients had recurrences and 20% had tumor progression. Although the limited sample precludes definitive conclusions, small tumor size, low-grade cytology, and low mitotic index appeared to be associated with an indolent behavior.

Use of 68Ga-FAPI PET/CT for Evaluation of Peritoneal Carcinomatosis Before and After Cytoreductive Surgery

ABSTRACT

A 55-year-old woman underwent 18F-FDG and 68Ga-FAPI PET/CT for tumor detection and staging under the prospective study NCT04416165. Both scans showed a mass lesion with increased tracer uptake in the pancreas. Moreover, 68Ga-FAPI PET/CT showed a greater number of abnormal foci in the mesentery and omentum than that shown with 18F-FDG. These abnormal foci were suspected to be metastases from pancreatic cancer. The patient subsequently underwent a cytoreductive surgery, and postoperative histopathology confirmed the diagnosis of acinar cell carcinoma of pancreas. Follow-up 68Ga-FAPI PET/CT (3 months after surgery) showed an excellent response with decreasing 68Ga-FAPI activity in the whole abdomen.