Mast cell and eosinophil interaction in gastric carcinomas: ultrastructural observations.

BACKGROUND: An increase in the number of mastocytes has been described in some human neoplasms, mainly in gastric and colorectal cancer. MATERIALS AND METHODS: A case of diffuse-type gastric carcinoma, mainly infiltrated by eosinophils and mast cells, was studied using light and electron microscopy. RESULTS: Using light microscopy, cell clusters containing one mast cell and one to three eosinophils were found in the tumour stroma. Electron microscopy of this unusual stromal element revealed that mast cells established areas of junctions with eosinophils. Moreover, focal polarized exocytosis of mast cell granules was found in the areas of junctions with eosinophils. Eosinophils in contact with mast cells showed signs of important in situ activation, such as alterations in the size and number of granules, cytoplasmic vacuoles, and scattered extracellular granules. CONCLUSION: Our ultrastructural study provides morphological evidence of cross-talk between activated mast cells and eosinophils that may play an important role in the enhancement of host immunity against cancer cells.