Mesenteric and omental cysts, arising between their peritoneal layers, are infrequent lesions but they have to be considered in case of expansive abdominal process because of the difficulty in diagnosis and choice of treatment.Often, they are occasionally founded and characterized by aspecific symptoms and radiological and echografic unclear pictures. The treatment of choice in represented by a radical exeresis and a definitive diagnosis is almost ever surgical and histopathological even if their nosological classification would be difficult for the pathologist too.The Authors report a case of cystic neoformation localized in the sovramesocolic lodge, between left hepatic lobe and less gastric curve, underling the diagnostic problems linked to a clinical and radiological picture with no univocal interpretation. The preoperative differential diagnosis, in fact, was in doubt between a post-traumatic pancreatic pseudocyst and a cyst of different origin.The intraoperative aspect excluded the pancreatic origin and oriented to the hypothesis of a gastric cystic duplication, in the lesser epiploon contest, originated from the lesser gastric curve and the gastro-oesophageal junction. The neoformation wasn’t dissociable from the gastric wall’s muscular tunica.A radical exeresis was preformed associated with a partial resection of the lesser gastric curve and gastro-oesophageal junction.The pathological examination, confirming the difficult nosologic classification of these lesions, gave a different interpretation excluding the hypothesis of a gastric duplication because of the absence of a surface epithelium in the lesion’s lumen
