Submitting Author: Li, Shaoying, MD
Institution: Vanderbilt University School of Medicine
Additional authors:Daniel J Long
Session: Erythroleukemia and megakaryoblastic AML and mimics

The patient is a previously healthy 60-year-old male who presented with pancytopenia with low normal serum vitamin B12. A marrow biopsy was performed in an outside institution and diagnosed as megaloblastic anemia with no cytogenetic study performed. He presented 2 months later with persistent pancytopenia despite vitamin B12 and folic acid supplement treatment with high than normal levels.

A marrow biopsy was performed and fixed in B-plus fixative. The outside marrow slides were reviewed. Peripheral blood smears from both time points showed normocytic, normochromic anemia with no hypersegmented neutrophils or giant bands. The aspirate and touch preparations are hypocellular, aparticulate and hemodiluted and consist predominantly peripheral blood elements. Compared to the first outside biopsy (80% cellularity, scattered to small clusters of increased immature erythroids), the current marrow is markedly hypercellular (>95%) with large clusters of immature erythroid blasts, represents > 80% of marrow cellularity. Megakaryocytes are adequate in number with dysplasia (small, hypolobated). Myeloid elements are rare with maturation. Plasma cells are not increased. There are rare interstitial small loose lymphoid aggregates composed of small mature lymphocytes.

Flow cytometry: performed on the hypocellular, aparticulate and hemodilute aspirate specimen and showed increased immunophenotypically unremarkable NK cells.

Immunohistochemistry and special stains: Immunohistochemical stains were performed using antibodies to CD34, CD61, CD117, glycophorin A, MPO, and E-cadherin. The large immature cells are positive for CD117, E-cadherin and glycophorin A, but negative for MPO, CD34 and CD61. CD34 is only positive in endothelial cells. MPO highlight rare scattered myeloids. CD61 highlights small hypolobated megakaryocytes. Reticulin stain demonstrated focal mild reticulin fibrosis.

Complex karyotype: 51~55,XY,-Y,+1,+2,+4,+4,+6,-7,add(7)(p13),+8,i(8)(q10),+10,+13,der(13;14)(q10;q10),add(17)(q25),+19,add(19)(p13.3)x2,+21,+22,+1~3mar[cp10]/46,XY[10]

MDS FISH Panel (chromosome 5, 7, 8, 20):

Abnormal for 3 copies of centromere 8 in 14.5% of cells.

None

This case demonstrate the differential diagnosis between acute erythroid leukemia and megaloblastic anemia can be quite challenging sometimes. Although increased immature erythroids and dysplastic features can be seen in both, megalablstic anemia usually has macrocytic anemia, hypersegmented neutrophils and /or giant bands, normal karyotype, and cytopenia quickly respnding to Vitamin B12 and folic acid supplement. Careful morphologic evaluation and cytogenetic karyotypic study is very important for a correct diagnosis.

Pure erythroid leukemia

Peripheral blood showed no circulating nucleated RBCs. The patient received 7+3 induction chemotherapy, showed persistent disease. The patient was then treated with 5+2 chemotherapy and achieved remission. However, while waiting for transplant, disease relapsed, and patient died. A total of 8 months of survival.

Acute erythroid leukemia (pure erythroid leukemia)

Case 63