Adenocarcinoma of the stomach with invasion limited to the muscularis propria

Adenocarcinoma of the stomach having invasion limited to the muscularis propria with or without lymph node metastasis, termed PM (proper muscle) gastric cancer by Japanese investigators, has a prognosis superior to that of carcinoma extending to the serosa and approaching that of early gastric cancer in Japan. To evaluate the occurrence and significance of PM gastric cancer in the United States, we analyzed 272 gastric carcinomas resected at our institution between 1964 and 1983. Forty-two PM cancers (15%) were identified. Improved 5-year survival rate was noted for PM cancer when compared with survival rate for 215 neoplasms exhibiting serosal invasion (29% versus 7%, P < 0.001). In univariate analysis, a survival advantage was also associated with absence of lymph node metastasis, intestinal-type histopathology of the Lauren classification, the expanding pattern of the Ming classification, and polypoid or fungating gross configuration of tumor. In multivariate analysis, depth of tumor invasion remained significantly associated with improved 5-year survival rate independently of other variables, including lymph node metastasis. Using continuous survival curves, the prognostic significance of PM cancer prevailed throughout the 5-year postgastrectomy interval. Our data indicate that PM gastric cancer occurs in the United States and need not be considered “advanced” gastric carcinoma; depth of tumor invasion should be recognized as a nodal metastasis-independent prognosticator of gastric cancer survival.