Histopathological and immunohistochemical aspects of mastocytosis.

The diagnosis of mastocytosis is based on histological evidence of a focal increase in tissue mast cells. Immunohistochemical staining with antitryptase antibodies is strongly recommended in all cases of suspected mastocytosis because mast cell infiltrates may be small and scanty. Mastocytosis may be difficult to distinguish from other hematological malignancies, in which an increase in mast cells is frequently seen. The expression of the T cell-associated antigen CD2 has been shown to be exclusively found on neoplastic mast cells in mastocytosis. The demonstration of expression of vascular endothelial growth factor by mast cells is consistent with the finding of angiogenesis which is commonly seen in tissue infiltrates of mastocytosis.