University of Virginia Health System

Immature Megakaryocyte
(Early Granular Megakaryocyte, Promegakaryocyte)

Bone marrow aspirate smear, Wright-Giemsa stain, 1000x

Description:

The earliest and clearly recognizeable megakaryocyte seen by light microscopy on a Wright-Giemsa stained bone marrow aspirate is best referred to as an immature megakaryocyte. It is larger than any other bone marrow cell, the nucleus often is starting to lobate, the nuclear chromatin is coarse and evenly dispersed, and one or more nucleoli are usually visible. The most chatracteristic feature is the presence of multiple cytoplasmic projections of variable length and distribution on the cell surface. The cytoplasm is deep blue (basophilic) and cytoplasmic granulation is minimal. An earlier megakaryocyte precursor occasionally is seen (megakaryoblast) and differs only in lacking cytoplasmic granulation, and having less nuclear lobation.

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