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Plasma cell versus osteoblast on bone marrow aspirate.

Plasma cells and osteoblasts are sometimes confused on bone marrow aspirate smear morphology.  Although both have eccentrically placed nuclei and can feature a pale paranuclear Golgi zone, note the clumped chromatin pattern of the plasma cell (sometimes described as a ‘spoke wheel’ or ‘clock face’).  Frequently the nuclei of osteoblasts appear partially extruded from the cytoplasm (Wright-Giemsa).