A Case of Retroperitoneal Benign Multicystic Peritoneal Mesothelioma

Abstract

A 39-year-old man was referred to our hospital with an intra-abdominal tumor detected via abdominal ultrasonography during a complete medical checkup. CT showed a 115×82mm, well-demarcated tumor with solid and cystic components in the retroperitoneum. The tumor was in contact with the gastric cardia, spleen, pancreatic tail, and left adrenal gland. PET-CT revealed FDG accumulation in the solid component. We performed ultrasound-guided transgastric puncture needle biopsy to retrieve the tumor specimen. Immunohistochemistry suggested that the tumor was derived from mesothelial cells ; however, malignancy could not be ruled out. We performed laparotomy and lumpectomy. Histopathological examination showed no malignant findings, and the patient was diagnosed with benign multicystic peritoneal mesothelioma (BMPM). Although BMPM is a benign tumor, it may recur, so that long-term follow-up is required. In previous literature, BMPM arising from retroperitoneum is rarely reported. In the present case, we were able to make a pathological diagnosis that the tumor was benign, but PET-CT showed a high degree of FDG accumulation ; therefore, it was difficult to confirm whether the tumor was definitely benign.