Increased proportion of CD25+ mast cells 2017-09-04T11:55:41Z An increased proportion of mast cells are positive for the cell surface marker CD25 (also called interleukin-2 receptor alpha chain). Mast cells do not normally express CD25, but neoplastic mast cells may be CD25-positive. Aberrant expression of CD2 and/or CD25 by bone marrow, peripheral blood or other extracutaneous tissue mast cells is currently used as a minor World Health Organization diagnostic criterion for systemic mastocytosis. CD25 expression alone presented a similar sensitivity (100%) with a slightly higher specificity (99.2%). Abnormal mast cell morphology