Benign multicystic peritoneal mesothelioma: a rare cause of intra‐abdominal cystic disease
A 49‐year‐old woman presented with abdominal pain for investigation. She had a background of chronic back pain, reflux, plantar fasciitis and obstructive sleep apnoea.
On presentation, her pain had been present for 3 months. It was mainly in the epigastrium, initially intermittent but now constant and exacerbated by eating. There was also weight loss of several kilograms over the past 6 months in addition to bloating. She reported neither diarrhoea nor constipation. There was no relation to any particular type of food.
Computed tomography (CT) of her abdomen showed a small quantity of free fluid in the right hepatorenal pouch and a suggestion of a small nodular density in the region of the greater omentum related to the inferior wall of the stomach close to the pylorus. An upper abdominal ultrasound and pelvic ultrasound were both normal. The full blood count, electrolytes, erythrocyte sedimentation rate and tumour markers including the CEA, CA19‐9 and CA‐125 were all normal. An endoscopy and colonoscopy were both normal.
Due to worsening symptoms, she was taken to theatre for a diagnostic laparoscopy. At laparoscopy, multiple cystic nodules were found on the greater omentum (Fig. 1) in addition to a cystic nodule on the right ovary (Fig. 2). The appendix appeared normal. An appendicectomy and right oophorectomy were performed in addition to excision of multiple cystic lesions arising from the greater omentum. Histopathological examination of the resected tissue confirmed the diagnosis of BMPM (Fig. 3).
BMPM, or multilocular peritoneal inclusion cysts as they are otherwise known, may arise from the serous pleural, pericardial or peritoneal lining. They occur most frequently in women of child‐bearing age, although several cases in men and children have been reported.5 An association between BMPM and chronic irritants of the peritoneum has been described, and as such, a history of pelvic inflammatory disease, endometriosis and previous abdominal surgery appear to be common themes in the reported cases.2
Debate regarding the exact nature of BMPM abounds: some authors argue for a neoplastic origin and some for an inflammatory reaction. Evidence for both exists and, currently, it is classified as an intermediate‐grade tumour that likely represents a lesion that lies on the border between an adenomatoid tumour and a malignant mesothelioma.2 There is no relation to prior asbestos exposure.
Vague and intermittent abdominal pain, tenderness or distension in association with a pelvic or abdominal mass are common presentations. Often the diagnosis of BMPM is made incidentally at surgery. Multiple cysts forming a confluent mass are often found, although free floating cysts have been reported. Involvement of the serosa of the bowel and the pelvic peritoneum are the most common findings. Histopathological analysis of these lesions reveals sheets of mesothelial cells lining the cysts, which are filled with an eosinophilic, serous fluid. Mesothelial hyperplasia may be present in foci and this finding can be confused with conditions such as viral infections and connective tissue disorders.
The diagnosis is exceedingly difficult to make on the basis of imaging alone and differential diagnoses include cystic hygroma, adenomatoid tumours, endometriosis, malignant mesotheliomas and primary or secondary serous tumours involving the peritoneum. Ultrasound may be useful and demonstrates multiseptated anechoic cysts; however, CT is preferred. Information regarding the mass location and extent can be gleaned from CT. Ultimately, histological diagnosis is required.