Cronkhite-Canada syndrome (CCS) is a rare nonhereditary disorder with gastrointestinal polyposis and associated ectodermal changes. This report documents a 59-year-old Japanese man with CCS who underwent a total gastrectomy for gastric tumors. The resected specimen showed a huge gastric adenocarcinoma with numerous polyps throughout the stomach. The cancer was pathologically limited to within the mucosa and its histological structure resembled that of hyperplasia in CCS polyps, which led us to suppose that the carcinoma had arisen from hyperplastic CCS polyps. These results urged us to study the phenotypic expression of mucins, which revealed MUC2(-) and MUC5AC(+) and supported the diagnosis of the tumor as a gastric-type well-differentiate adenocarcinoma. A literature search revealed that 32 gastric carcinomas which developed in patients with CCS were mostly limited to within the submucosa in spite of their huge sizes, and such cancer development in CCS polyposis is therefore not considered to be unusual.