# Benign Cystic Mesothelioma of the Peritoneum Arising at the Greater Omentum in a 14-Year-Old Boy

## TL;DR

A 14-year-old boy was diagnosed with a rare benign peritoneal mesothelioma, highlighting the need for careful differentiation from lymphatic malformations in children.

## Contribution

This paper presents an extremely rare pediatric case of benign cystic mesothelioma of the peritoneum.

## Key findings

- The tumor was macroscopically misdiagnosed as a benign omental lymphangioma but was confirmed as mesothelioma via histopathology.
- Immunohistochemistry showed calretinin reactivity, supporting the diagnosis of mesothelioma.
- The case emphasizes the importance of considering mesothelioma in the differential diagnosis of pediatric abdominal cystic lesions.

## Abstract

Mesothelioma arises from mesothelial cells. This tumor is very rare among pediatric abdominal neoplasms. We herein report an extremely rare case of acute abdomen with cystic mesothelioma of the peritoneum in a child.

A 14-year-old boy was referred to our hospital for emergency surgery. Surgery revealed a primary tumor arising from the greater omentum. The tumor was macroscopically diagnosed as a benign omental lymphangioma and was resected en bloc with the greater omentum. A histopathological examination of the tumor revealed a simple columnar epithelium-like mesothelioma with poor cell-atypia. Immunohistochemical examination showed antibody reactivity in the cyst epithelium, including an anti-calretinin antibody. The final pathological diagnosis was a mesothelioma originating from the peritoneum.

In pediatric cases diagnosed with cystic lymphatic malformation, the possibility of peritoneal mesothelioma needs to be considered and carefully confirmed or ruled out.