A 50-year-old woman had a right hemicoletomy due to a large sessile polyp in the ascending colon, inappropriate for polypectomy. Histopathologic examination of the specimen showed a tubulovillous adenoma with moderate dysplasia and an adjacent 1 x 1 cm submucosal tumor classified as a benign GCT due to the appearance in the light microscope and immunohistochemical analysis. To our knowledge, this is the first reported case of synchronic adenoma and GCT in the colon. To date there is no evidence of any association or disposing factors between GCT in the colon and colonic adenomas or malignancy.