Macropolycytes are not necessarily dysplastic since they are occasionally seen in the blood films of healthy subjects and can appear cytologically normal—apart from being double normal size with a proportionate increase in the size of the nucleus, the degree of nuclear lobulation and, in women, the number of nuclear drumsticks. They have been shown to be tetraploid and thus represent a missed cell division. These cells are increased in number in myeloproliferative neoplasms, during infection and following growth factor administration. They occur also in megaloblastic anemia and HIV infection, when they may show additional cytological abnormalities, including a more open chromatin pattern. Macropolycytes are an uncommon feature of the myelodysplastic syndromes (MDS) and myelodysplasia-related acute myeloid leukemia (AML). The macropolycytes shown here are from a 67-year-old man with myelodysplasia-related AML, who had initially presented 19 months earlier with MDS (specifically refractory cytopenia with multilineage dysplasia).

The left hand image shows a macropolycyte flanked by two neutrophils of normal size. All three cells are hypogranular and in addition the upper cell shows an acquired Pelger–Huët anomaly. The nucleus of the macropolycyte is abnormal in shape. The top right image shows two binucleated macropolycytes, one of which has hyperchromatic nuclei while the bottom right image shows a hypogranular binucleated macropolycyte, with both nuclei showing an acquired Pelger–Huët anomaly.

Dysplastic macropolycytes can occur in reactive conditions and deficiency states but should be recognized as an uncommon feature of myeloid neoplasms, including MDS and AML.