Which doc should one consult for 20 cm by 20cm cyst in stomach for removal

First family doctor: See your family doctor first for evaluation and diagnosis of cyst , most likely it is out side the stomach like pseudo or true cyst of pancreas, depending on the nature of it some need observations others drainage by GI (endoscopic) or removal by surgeon your doctor will advise you and then you decide.

Experience is key: You should find a doctor who is appropriately trained and with whom you are comfortable. I would recommend a surgical oncologist. In addition to standard training in general surgery (a minimum of five years), these physicians typically receive from two to three years of additinal training in complex tumor surgery. Check www.Surgonc.Org to find a surgical oncologist near you.