Molecular analysis revealed a <i>KIT</i> D816V mutation consistent with a diagnosis of systemic mastocytosis, mast cell leukaemia.<h4>Conclusion</h4>The expression of T-cell associated markers by abnormal mast cells is well documented; however, CD4 and CD7 expression have not previously been described in association with mast cell leukaemia. The gene discussed is KIT; the disease is mast cell leukemia.