Plasma cell leukemia with an unusual karyotype and prolonged survival with oral alkylating agent therapy.

A patient with primary plasma cell leukemia (PCL) is presented, who had an excellent response to high-dose cyclophosphamide and prolonged survival. The sole cytogenetic abnormality detected in the bone marrow was monosomy 18. Although this karyotypic aberration has been previously described in PCL, it generally occurs associated with additional abnormalities. The peripheral blood plasma cells from this patient reacted intracellularly with the monoclonal antibody OKM-1, which binds to myeloid cells at and above the level of myelocytes and to monocytes. This finding supports the idea of a common precursor cell for plasma cells and cells of the myelomonocytic lineage.