CD2 and systemic mastocytosis: Similarly, in a recent trial based on a small number (n = 10) of imatinib-treated SM patients, a high CR rate (40%) was reported, but only for patients carrying mutations in the extracellular region of KIT (K509I) (n = 3) or with wild-type KIT (n = 1), typically with a unique CD25− and CD2− phenotype [27], and that represent a minor fraction (≤5%) of all (indolent and advanced) SM cases [11].