Utility of Flow Cytometric DNA Ploidy Analysis in the Diagnosis of Pure Erythroid Leukemia: An Illustrative Case Report

Introduction: The classification and definition of leukemic proliferations pertaining to erythroid lineage have undergone modifications since their first description in the early 19th century. Pure erythroid leukemia (PEL), despite the stringent current WHO definition, is a difficult diagnostic entity owing to problems in distinction from non-neoplastic and neoplastic mimics and lack of lineage specific flow cytometry (FCM)/ immunohistochemistry (IHC) markers. However, almost all the cases of PEL have complex cytogenetics with chromosomal aneuploidy.

Case Study: Here we present a case of 54 year male, known case of Polycythemia Vera since 12 years who developed pain in both the lower limbs for the past 10 days. Peripheral blood smear revealed leuko-erythroblastic picture. With the clinical query of myelofibrosis/ leukemic transformation, bone marrow examination was done. Both aspirate and biopsy revealed marked erythroid hyperplasia with many cells having immature proerythroblastic morphology. Flow cytometric immunophenotyping revealed 35% erythroid cells expressing CD58 and CD71 along with 5% myeloid blasts expressing CD34, CD38, CD117, CD71, CD13, CD33, HLADR along with dim myeloperoxidase (MPO) and aberrant CD7. FxCycleTM violet (FCV) based FCM DNA ploidy, performed as a part of routine, revealed a major high-hyperdiploid clone with DNA Index (DI) 1.35 and minor diploid clone with DI 1.01 for both erythroid cells and myeloid blasts. Cytogenetic analysis also confirmed both these clones with a modal karyotype 58~63,XY,-5,-7,-12,-14,-17,-20,+21[cp16]/46,XY[4]. Karyotype analysis is technically challenging and not available at many centres.

Discussion and Conclusions: FCV based FCM DNA ploidy is a rapid, simple and inexpensive assay which has strong correlation with cytogenetic ploidy and can provide specific results in immunophenotypically selected cells, in hemodilute samples, even in cases with cytogenetic culture failure and can supplement the diagnosis of PEL.