CD44 and systemic mastocytosis: For instance, the mRNA levels of the receptors CD44 and CXCR4, significantly downregulated in HMC-1.3 compared to HMC-1.2 (Table 1), are important for homing of stem cells, huMCs and/or huMC progenitors (46–48, 60) and have been associated with hematological malignancies, including systemic mastocytosis (47, 61, 62).