INCREASED INCIDENCE OF UNDIFFERENTIATED TYPE OF GASTRIC-CANCER WITH TUMOR PROGRESSION IN 912 PATIENTS WITH EARLY GASTRIC-CANCER AND 1245 WITH ADVANCED GASTRIC-CANCER

Background. There is little information concerning alteration in histologic differentiation with progression of gastric cancers. Methods. The authors analyzed data of 912 patients with early gastric cancer and 1245 with advanced gastric cancer. All patients underwent gastric resection. Special focus was placed on the grade of histologic differentiation. Results. The undifferentiated type was found in 38% of early gastric cancers and 58% of advanced gastric cancers (P < 0.01). The undifferentiated type was found in 37% of gastric cancers limited to the mucosal layer, and increased with tumor progression into the deep layer to account for 65% of the cancers that invaded the gastric serosa. With regard to tumor location, the undifferentiated type in the gastric body or other locations was more common in patients with advanced gastric cancer (P < 0.01). Conclusions. One explanation for the histologic predominance of the undifferentiated type in advanced gastric cancer is that in some gastric cancers, the predominant histologic type may be altered from the differentiated to the undifferentiated type with progression of the tumor.