Abstract
Simultaneous gastric cancer in identical twins is reported. We operated on a female patient whose lesion was similar in location, macroscopic type and microscopic type to that of her twin sister although extension of their lesions were very different. Only 8 pairs of gastric cancer in identical twins have been reported in Japan. Most authors have emphasized hereditary factors. We did not consider heredity to be important because the number of reports is very small in Japan where gastric cancer is very common. Past reports have shown that lesions in identical twins resemble each other macro and microscopically. We speculate that the resemblances are due to the same genes at brith and the accumulation of similar genetic mutations after birth.
