Part 2: Answer: Haemorrhagic mesenteric cyst

The lesion was surgically removed. At microscopic analysis, the cyst wall contained fibrous tissue without an epithelial lining, consistent with a haemorrhagic mesenteric cyst of non-neoplastic origin (non-pancreatic pseudocyst). Mesenteric cysts form a heterogeneous group of rare intra-abdominal cystic lesions, situated in or near the mesentery and without connection to retroperitoneal structures. Incidence varies from 1/20 000 to 1/100 000 hospital admissions according to the age of the patient, with more frequent diagnosis in younger patients.1 Various classifications have been proposed based on the aetiology of the cystic structure, distinguishing embryonic and developmental cysts from lesions of traumatic, neoplastic and infectious origin. As most of these older classifications are confusing, the current classification of mesenteric cysts is essentially based on histopathological characteristics of the tissue or structure from which they derive.2 Cysts …