Frequency of Atypical Mitosis in Intestinal Metaplasia of the Gastric Mucosa in Japanese Patients

The morphologic characteristics of the mitotic figures present in intestinal metaplasia (IM) of the gastric mucosa were investigated in 70 concecutive gastrectomy specimens from Japanese nationals. The specimens contained, in addition, early gastric cancer of intestinal type (n=44) or of diffuse type (n=22). The remaining 4 were recorded as mixed. One hundred or more consecutive mitoses/specimens were studied by high‐power microscopy in hematoxylin and eosin‐stained preparations (at × 1000). A total of 7259 mitoses were recorded (mean 103.7 mitoses/case). Of these, 1089 mitoses (i.e. 19.1%) were considered as atypical according to a previous classification. The percentage of atypical mitoses was found to be unrelated to the gender, to the increasing age of the patients, to the histologic type of the adenocarcinoma contained in the specimens, or to the anatomic site (e.g. corpus or antrum or tumor proximity). Comparative studies were done with gastrectomy specimens from Swedish nationals (a population with a 4‐times‐lower incidence of gastric carcinoma than the Japanese). The results showed a much lower frequency of mitotic figures/specimen and only occasional atypical mitosis. Since atypical mitosis has so far been reported only for neoplastic lesions in the gastrointestinal tract, it is suggested that IM with atypical mitosis may be a genuine precancerous lesion in the gastric mucosa in Japanese subjects.