Mast cells

They have many similarities to basophils. Masts cells are usually noted in tissue and bone marrow but absent from peripheral blood (unlike basophils which are in bone marrow and peripheral blood). Mast cells can release substances such as histamine in allergic reactions. Neoplastic mast cells cause cutaneous and systemic mastocytosis. Both normal and abnormal mast cells are typically positive for Mast cell tryptase and CD117 (C-Kit). However, most abnormal mast cells may aberrantly express CD2 and CD25 (T-cell markers).