A RARE CASE OF MULTILOCULAR PERITONEAL INCLUSION CYST IN A MALE PATIENT.

Editor,

Multilocular peritoneal inclusion cysts (MPIC) are uncommon lesions, of which only around 20% of cases are reported in adult men. The mesothelial origin of MPICs was first demonstrated by electron microscopy in 1979, by Mennemeyer and Smith.1 MPICs can occur anywhere along the peritoneal surface, arising from the peritoneal mesothelium, but are most frequently found in the pelvis as multiple, thin-walled, multi-locular cysts, that can form large intra-abdominal masses.2,3 A 41-year old man presented as an emergency with a short history of pelvic pain and discomfort. He complained of bladder and rectal symptoms including difficulty bladder voiding and marked tenesmus. The patient’s past medical history includes Guillain-Barre syndrome secondary to CMV infection. CT and MRI scan showed a large mass between the rectum and bladder (Figure 1) measuring 8.6x8.5x8.5cm. A flexible sigmoidoscopy was performed and no mucosal abnormality was detected. Blood test and tumour markers (CA125, PSA, CEA, CA19-9 and AFP) were all within normal limits. At laparotomy, a large multi-cystic mass was situated between bladder and rectum. The mass appeared to arise from the mesentery of the sigmoid colon (Figure 2). Therefore, in addition to resection of the multi-cystic mass, a sigmoid colectomy with a primary anastomosis and an appendicectomy were performed. No other abnormality was detected in the rest of the colon, small bowel, stomach or gallbladder. Pathology showed a large multi-cystic mass measuring 112 x 87 x 47mm and weighing 290g. On sectioning, the mass consisted of numerous thin-walled cysts of varying size containing serous fluid. Histopathology showed a multilocular peritoneal inclusion cyst; each locule was lined by bland mesothelial cells and the septae contained fibrovascular connective tissue with a chronic scattered inflammatory cell infiltrate (Figure 3). There was no malignancy Using immunohistochemistry the cells lining the cysts were shown to express WT1 and CK5/6 in keeping with mesothelial lineage. Within the distal sigmoid colon specimen, there was a localised area of haemorrhage and a separate 12mm diameter nodule of multi-locular peritoneal inclusion cyst was present on the serosal surface. The appendix showed pinworm infestation but no evidence of dysplasia or invasive malignancy. The patient made a good post-operative recovery and was discharged home six days after surgery. The patient was reviewed 6-weeks after surgery and all symptoms had resolved. A repeat CT scan of his abdomen and pelvis, 6 months after surgery showed no recurrence. We plan for annual patient follow-up. MPIC are generally considered a benign reactive mesothelial proliferation developing secondary to endometriosis, trauma, inflammation or pelvic inflammatory disease (2,3). This patient cohort would suggest that MPIC is a reaction to chronic irritation stimuli with mesothelial cell entrapment, reactive proliferation and cystic formation. Some consider MPIC to be mesothelial neoplasms with the potential for malignant transformation. The uncertainty and debate surrounding these lesions is reflected by the limited evidence available.3,4 MPIC has a high rate of local recurrence and surgical resection remains the mainstay of treatment to avoid local recurrence. 5 It is this infrequency, which makes its origin, pathogenesis, diagnosis and therapy challenging.

Figure 1

MRI Pelvis

Figure 2

Dissected multi cystic mass

Figure 3

Numerous cysts lined by bland mesothelial cells with fibrovascular septa containing chronic inflammatory cells