The first identified mammalian HAS gene, HAS1, produces a full-length transcript (HAS1-FL) and three variants (HAS1-Va, HAS1-Vb, HAS1-Vc), which are linked to poor survival in malignant myeloma and Waldenström’s macroglobulinemia. Here, HAS1 is linked to Waldenstrom macroglobulinemia.