Gastrointestinal stromal tumour masquerading as a cyst in the lesser sac

Gastrointestinal stromal tumours (GISTs) are solid tumours of the gastrointestinal tract, mostly found in the stomach and intestine. They rarely present as cystic lesions. A 74-year-old woman referred to the hepatopancreaticobiliary unit, with 3 months history of upper abdominal discomfort. Abdominal ultrasound scan showed a large cystic lesion in the epigastric region suggestive of a pancreatic pseudocyst. The CT-scan showed a 6.6×6×6.3 cm size cyst related to the pancreas and extending to the hepatogastric omentum. Endoscopic ultrasound (EUS) scan was suggestive of a pancreatic pseudocyst. Aspirated Cyst fluid via EUS showed benign cytology with normal amylase, lipase and tumour markers (CEA, CA-19.9 and CA-125). She was referred as a case of pancreatic pseudocyst. After surgical excision, the histopathology confirmed the presence GIST in the wall of the cystic lesion. The possibility of GIST should be kept in mind in the presence of unusual features of a cyst on abdominal imaging.