The plasmacytoid portion of the tumor cell clone typically expresses cytoplasmic IgM that is secreted into the serum, in conjunction with B cell markers; for example, CD19 and CD45 (protein tyrosine phosphatase, receptor type, C or PTPRC) and plasma cell markers; for example, CD38 (cyclic ADP ribose hydrolase) and CD138 (syndecan 1). The gene discussed is CD19; the disease is neoplasm.