Perivascular mast cells in advanced gastric adenocarcinomas: an electron microscopic study

Mast cells are frequently found in close proximity to blood vessels and have been implicated in tumour angiogenesis. The aim of the present ultrastructural study was to characterize, in detail, the mutual association between mast cells and microvasculature in 9 cases of advanced gastric carcinoma. Perivascular mast cells were ultrastructurally identified as T mast cells and exhibited piecemeal degranulation, indicative of a slow release of granule-stored contents. In two cases they were adjacent to endothelial cells showing vesiculo-vacuolar organelles, a newly-defined endothelial cell permeability structure. Collagen fibres and dispersed fibrous long-spacing collagen were found near T mast cells in one case, suggesting their role in perivascular collagen degradation and/or turnover. Mast cells were associated with microvascular basal lamina changes including irregular thickness, multiple layers and loose association with endothelial cells and pericytes, reminiscent of degenerating or regenerating blood vessels. In conclusion, our ultrastructural study suggests that mast cells contribute to the remodelling of existing vessels by a slow release of granule-stored contents in advanced gastric adenocarcinomas.