Eosinophil-tumor cell interaction in advanced gastric carcinoma: An electron microscopic approach

BACKGROUND: Tumor-associated tissue eosinophils have been observed in human tumors and experimental tumor models, but their function is poorly understood. MATERIALS AND METHODS: One case of intestinal-type adenocarcinoma of the stomach, mainly infiltrated by eosinophils, is studied by light and electron microscopy, focusing on the relationships between eosinophils and tumor cells and on the nature of tumor cell death. RESULTS: Using light microscopy, eosinophils, single or in clusters, were present both in the stroma and within neoplastic glands. With electron microscopy, tumor cells in intimate contact with eosinophils revealed changes consistent with autophagic cell death such as chromatin condensation in small masses into the nucleus, dilation of the nuclear envelope, and numerous cytoplasmic vacuoles. The adenocarcinoma cells, not contacted by neutrophils, remained morphologically well preserved. CONCLUSIONS: Our ultrastructural study suggests the hypothesis of a direct relationship between eosinophil infiltration and induction of autophagic cell death in gastric adenocarcinoma cells.