The peripheral blood smear of patients with plasma cell leukemia demonstrates a leukocytosis with circulating plasma cells. By definition, the absolute plasma cell count must exceed 2000/microL or 20 percent of the peripheral white blood cell count. The morphological features of plasma cells can differ depending upon their maturity. Mature plasma cells are oval with abundant basophilic cytoplasm. The nucleus is round and eccentrically located with a marked perinuclear hof, or cytoplasmic clearing.