Gastric carcinoma occurring simultaneously in monozygotic twins has been reported only three times. Two pairs of twins with cancer of the stomach were reported by Macklin1 from the European literature, while Militzer2 reported the only cases in the American literature in 1935.
We have had the opportunity to study an interesting pair of monozygotic twins in whom cancer of the stomach was apparently present simultaneously, although symptoms began and deaths occurred nearly a year apart. As will be shown, the cancers were not identical, histologically, but both were adenocarcinomas arising in the gastric mucosa. Every effort was made to determine the zygosity of these women, since there is no reported case known to us of gastric carcinoma occurring simultaneously in dizygotic twins. These women were considered monozygotic on the basis of their statements that they were often confused even by members of their own family, that their thinking