In the walls of the stomac & in the tail of the pancreas a solid formation 12cm, a tumor. can be a gist?can be operated?what to do?

Could be, need test: Gastrointestinal stromal tumors (GIST) are be either malignant or benign. However a 12 cm lesion is more likely to be malignant and needs additional testing including an endoscopy with ultrasound and biopsy (usually done by a gastroenterologist). Depending on pathology analysis, either Glevac can be used alone or with surgery. See a surgical oncologist if this is a malignant GIST.