The mixed type in Laurén's classification of gastric carcinoma. Histologic description and biologic behavior.

Of 198 gastric carcinomas, resected at the Surgical Department, Leipzig University between 1986 and 1995, 28 cases were classified as mixed type according to Laurén's classification. These cases were examined in respect to morphologic features associated with biologic behavior. Contrary to the intestinal and diffuse type carcinomas, the mixed type carcinomas showed a deeper infiltration of the gastric wall (pT, P < 0.001), a higher metastatic rate to regional lymph nodes (pN, P < 0.05), and the need of higher staging at the UICC-classification system (P < 0.05). Histologically, it is possible to establish four distinct groups; the first group shows a combination of intestinal and diffuse features, the second shows more diffuse structures with a nodular growth pattern, the third group shows both a glandular pattern and signet ring cells. In the fourth group, the tumors reveal an excessive production of mucin. The authors conclude that this subclassification of the mixed type of gastric carcinomas is useful for a better understanding and interpretation of these tumors.