Diagnostic evaluation and classification of mastocytosis

Mastocytosis is a term collectively used for a group of disorders characterized by abnormal accumulation of mast cells (MCs) in one or more organ systems. Cutaneous mastocytosis is a benign disease of the skin that usually manifests in early childhood and often regresses spontaneously before or during puberty. By contrast, systemic mastocytosis (SM) is a persistent disease of neoplastic MCs. In these patients, MC infiltrates are detectable in one or more visceral organs with or without skin involvement. In most patients with SM, the somatic KIT mutation D816V is detectable. The clinical course in SM is variable, ranging from an asymptomatic status for many years with a normal life expectancy to highly aggressive cases with a poor prognosis and short survival. The World Health Organization classification defines five categories of SM: indolent SM, aggressive SM, SM with associated clonal hematologic non-MC lineage disease, and mast cell leukemia. This article provides a summary of current markers, criteria, and tests used to diagnose mastocytosis and to discriminate between subvariants of the disease.