Ultrastructural descriptions of heterotypic aggregation between eosinophils and tumor cells in human gastric carcinomas.

A histological variant of gastric adenocarcinoma, characterized by an intense tumor-associated tissue eosinophilia (TATE), has been occasionally reported in the literature. The purpose of this ultrastructural study was to determine the interactions between frequently occurring eosinophils and tumor cells in gastric carcinoma characterized by TATE. Fresh tumor tissue of 92 gastric carcinomas was processed for both light and electron microscopic examination. Intense TATE was found in 7 out of 92 (7.6%) gastric carcinomas (6 of intestinal-type and 1 of diffuse-type). Electron microscopy, selectively performed in 7 cases with intense TATE, revealed eosinophils, singly or in groups, in contact with damaged or necrotic tumor cells. Activated eosinophils showing piecemeal degranulation were also found in intimate contact with viable tumor cells, characterized by plasma membrane caveolar invaginations. The authors regard this close morphological relationship as in vivo evidence for possible cross-talk between eosinophil and viable tumor cell, a conclusion that has already been drawn from experimental studies, but until now inadequately supported by ultrastructural observations in a human tumor.