Mast cells (MCs) always accompany connective tissue and are located inthe proximity of lymphatic and blood vessels and nerve fibers. They are round or oval mononuclear cellswith a diameter of 4-20 microm containing in their cytoplasm specific exocrine granules (storing neutralproteases) enclosed by a single membrane, whose presence is regarded as an index of the MC's static state.In view of their wide distribution in the organism, they play various roles in, for example, type I hypersensitivityreactions, chronic inflammatory processes, tissue reconstruction and wound healing, and pathologicalpulmonary fibrosis. They also play a role in angiogenesis, both in normal conditions during tissue regenerationand in pathological neoplastic states. The microcirculation provides building and nutritional substancesto cancer cells and enables cancer spread via the blood. On the other hand, a tumor with good vascularizationis more prone to penetration by cytostatics, which is why angiogenesis is a very important process inthe course of neoplastic disease. Many authors indicate a close association between mast cells and angiogenesis.Some substances contained in the cytoplasm of these cells are potent stimulators of angiogenesis (tryptase,heparin), while others may inhibit it (protamine, platelet factor 4), and this conditions cancer growthand the development of the metastatic process. It is not known, however, what interactions occur betweenstimulants and inhibitors and what the proportional involvement of particular mediators in the formationof new vessels is.

Keywords: Mast Cells - physiology, Neoplasms - blood supply, Neovascularization, Pathologic