Depressed type of intramucosal differentiated-type gastric cancer has high cell proliferation and reduced apoptosis compared with the elevated type

Background: The depressed type of early gastric cancer, in comparison to the elevated type, tends to invade the submucosal layer and metastasize to the lymph nodes. This study compared the differences in tumor cell proliferation and apoptosis between the elevated and depressed types of intramucosal differentiated gastric cancer. Methods: A total of 57 intramucosal differentiated gastric cancers were studied. Twenty samples were the elevated type and 37 were the depressed type. The tumor cells were analyzed by immunohistochemistry for Ki-67, Bcl-2, and Bax, and terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate (dUTP)-biotin nick end labeling was carried out to detect apoptotic cells. Results: (1) The Ki-67 labeling index (KI) was higher in the depressed type (median: 38.6) than in the elevated type (median: 21.2). (2) Immunopositivity for Bax and the apoptosis index (AI) were lower in the depressed type (median AI: 0.20) than the elevated type (median AI: 1.05). (3) The AI/KI was lower in the depressed type (median: 0.17) than in the elevated type (median: 5.57). (4) The AI in the tumors with a Bcl-2-negative and Bax-positive pattern (median: 2.0) was higher than that in the tumors with a Bcl-2-positive and Bax-negative pattern (median: 0.2). Conclusion: These results show that, regarding cell proliferation and apoptosis, the depressed type of intramucosal differentiated-type gastric cancer has high malignant potential in comparison to the elevated type.