A Mesothelial Inclusion Cyst Presenting in a 40-Year-Old Woman as Abdominal Pain and Bloating – A Rare Diagnosis

Cystic mesotheliomas (also called mesothelial inclusion cysts) are rare benign neoplasms that occur more often in young women. Symptoms are usually non-specific, demanding a thorough work-up. We report a case of a 40-year-old female patient with 2 prior caesarean sections presenting with a 3-month history of abdominal pain. Laboratory tests revealed microcytic hypochromic anaemia and an elevated tumour marker CA-125. An investigation identified a large cystic abdominal mass, mostly in the left side of the abdomen. A laparotomy was performed with total resection of the lesion. Histological assessment resulted in a diagnosis of a mesothelial inclusion cyst. The patient had no recurrence after 3 years. LEARNING POINTS: Peritoneal mesotheliomas are rare conditions, and with benign features are even rarer. Mesothelial inclusion cysts, also known as benign cystic mesothelioma, occur more often in young to middle-aged women with excellent prognosis, although there are high rates of local recurrence. Investigation unmasks large abdominal lesions. A timely diagnosis is of the utmost importance, to prevent a dramatic change in outcome if severe complications develop.