Benign Multicystic Peritoneal Mesothelioma Mimicking Acute Appendicitis: A Case Report

Background: Benign multicystic peritoneal mesothelioma is a rare tumor derived from mesothelial cells characterized by multiple thin-walled cysts attached to the peritoneal surfaces. It occurs more frequently in women and has been associated with previous abdominal surgery, endometriosis, or pelvic inflammatory disease. Despite its benign nature, it has a high recurrence rate after surgical treatment. Case presentation: We report the case of a 34-year-old male with a history of bilateral varicocelectomy and bilateral inguinal hernioplasty who presented to the emergency department with acute onset right lower quadrant abdominal pain suggestive of acute appendicitis. Laboratory tests showed elevated C-reactive protein levels. Abdominal computed tomography revealed multiple well-defined cystic lesions in the right lower abdomen and pelvis. Diagnostic laparoscopy was performed due to suspicion of a periappendiceal abscess, revealing a 6 × 4 × 2 cm multicystic tumor attached to the mesentery and right colon, along with multiple grape-like cystic lesions throughout the abdominal cavity. Local tumor resection, removal of most cystic lesions, and appendectomy were performed. Histopathological examination confirmed the diagnosis of benign multicystic peritoneal mesothelioma. Conclusion: This case highlights an uncommon presentation of benign multicystic peritoneal mesothelioma in a male patient mimicking acute appendicitis. Laparoscopy plays an important role in both diagnosis and treatment, allowing complete surgical resection. Long-term follow-up is recommended due to the risk of recurrence.