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 5% 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. The nucleus contains "clock-face" or "spoke wheel" chromatin without nucleoli. Immature plasma cells have dispersed nuclear chromatin, prominent nucleoli and a high nuclear to cytoplasmic ratio.
