We found a significantly reduced expression of GPER1 mRNA in symptomatic myeloma (MM) and in the more aggressive extra-medullary stages of plasma cell dyscrasias (PCL) with respect to normal PCs, or to PCs from MM pre-malignant conditions (MGUS and SMM), with the lowest expression observed in the HMCLs group (Figure 1A). Here, GPER1 is linked to plasma cell leukemia.