Immunophenotyping of mast cells: a sensitive and specific diagnostic tool for systemic mastocytosis.

INTRODUCTION The diagnosis of systemic mastocytosis (SM) is based on a combination of major and minor criteria. Flow cytometric detection of aberrant expression of CD2 and/or CD25 on CD117-positive mast cells is one of the minor criteria used. In the present study we examined the sensitivity and specificity of mast cell immunophenotyping in the diagnosis of SM. MATERIAL AND METHODS Patients were 36 persons with SM diagnosed according to WHO criteria. Controls were 31 patients without SM. Immunophenotyping was performed according to published guidelines. RESULTS All patients with SM were positive for CD2 and/or CD25. All patients without SM , except one, were negative for these markers. The sensitivity for immunophenotyping was 100%, the specificity 91%. The positive and negative predictive values were 97% and 100% respectively. CONCLUSION Immunophenotyping of bone marrow derived mast cells is not only a very sensitive but also a very specific method to diagnose SM with high positive and negative predictive value.