These populations include nucleated red blood cells (cells negative for all antigens commonly tested in myeloma MRD tube), mast cells (exceptionally bright CD117 with somewhat increased side scatter), early maturing B cells (hematogones) (CD19-positive cells with bright CD81 and CD38 without cytoplasmic light chain expression with relatively dim CD45), and early myeloid and erythroid precursors (CD117-positive, CD27-negative cells). Here, CD81 is linked to plasma cell myeloma.