Mast cells and skin tumors.

Mast cells are known as a major normal cellular constituents of dermal connective tissues. They contain an array of biologically active chemical mediators in their granule. Although physiological role of mast cells still remains unclear, they definitely play an important role in hypersensitivity reactions. Apart from typical mast cells in dermal connective tissues (connective tissue mast cells: CTMC), phenotypically distinct mast cell subpopulation, named mucosal mast cells (MMC), has been identified in intestinal and respiratory mucosa. Although phenotypic difference and compartmentalization of CTMC and MMC are clearly seen in mice and rats, our recent observations of Mongolian gerbil mast cells revealed that the phenotypes of mast cell subtypes in this animal was markedly different from those of mice and rats. Similar observation has been reported on human mast cell subsets. Since local mastocytosis or mast cell infiltration is frequently observed in various pathological conditions in the skin, such as ulticaria pigmentosa, neurofibromatosis, keroid, and malignant tumors, cautions should be paled for the characteristics of mast cells involved in the pathophysiology of dermal diseases.