Peritoneal inclusion cysts are rare benign cysts of mesenteric origin with less than 1000 cases reported in literature.  They are usually asymptomatic but can become symptomatic when they grow in size; can reach upto 40 cm in size  and when they undergo rupture, torsion or get infected.
They usually occur in women in reproductive age. There are several theories on their origin. One theory is that they arise from congenital incomplete fusion of peritoneal surfaces. Another theory is that they arise due to collection of fluid in peritoneal adhesions formed secondary to pelvic surgery / endometriosis / pelvic inflammatory disease.  The second theory holds good in our case since our patient had a previous Caesarean section, and fluid accumulation in the adhesions might have caused a peritoneal cyst which presented as hernia. Another theory is that it develops from proliferation of ectopic lymphatic in mesentery which does not have connection with the lymphatic system 
There are less than 10 reported cases of mesenteric cysts presenting as inguinal hernia.  Our case is the first case of peritoneal cyst presenting as incisional hernia, and clinically and radiologically masquerade as tubo-ovarian complex which turned out to be peritoneal inclusion cyst on histopathology. Owing to its rarity, it is difficult to diagnose it clinically and radiologically and histopathology is essential for confirming the diagnosis and also for excluding other malignancies.
When symptomatic, Peritoneal inclusion cyst should be excised completely, since incomplete excision can lead to recurrence.
To conclude, though extremely rare, it is important to consider Peritoneal inclusion cyst in differential diagnosis of contents of hernia since its incomplete excision can lead to recurrence.