Submitting Author: Jamali, Mina, MD MSc FRCPC
Institution: Sunnybrook Health Sciences Centre and the University of Toronto
Additional authors:Hubert Tsui
Session: Erythroleukemia and megakaryoblastic AML and mimics

The patient is a 59-year-old man with a past medical history significant for chronic hepatitis C infection with no prior liver biopsy or treatment sought. His history also includes several years of cytopenias, predominantly macrocytic anemia with elevated liver enzymes attributed to excessive alcohol intake which would normalize on abstinence. His case begins when he first presented to an outside hospital with a complaint of fatigue and was found to be severely anemic. Physical examination was unremarkable. A bone marrow study was performed and was reported to be hypercellular with a final diagnosis of refractory anemia with multilineage dysplasia and ring sideroblasts (RCMD+RS) with normal conventional cytogenetics. MRI imaging investigations revealed no hepatosplenomegaly but findings possibly indicative of diffuse fatty infiltration of the liver or hemochromatosis. Four months later and red blood cell transfusion dependent, he presents to our hospital with pancytopenia, night sweats and interim 30-pound weight loss. It was clarified that there had never been administration of erythropoietin (EPO).

A bone marrow study (BMS) was performed. Note, the initial study was not available for review.

Laboratory values from the same day as the BMS:

WBC 1.0x10^9/L, Hb 76g/L, Platelets 55x10^9/L,

Absolute WBC differential count (x10^9/L): neutrophils 0.3, lymphocytes 0.7

. HCT 0.219L/L, RBC 2.46x10^12/L, MCV 89.2fL, RDW 12.6%, MCH 31.0pg, MCHC 348g/L, Retic 7x10^9/L,

LDH 210I U/L, ferritin 5544 ug/L, Erythropoietin Assay 896 U/L.

Peripheral blood smear:

The peripheral blood smear shows severe pancytopenia. Circulating blasts are not identified. There is an absolute neutropenia and monocytopenia. The neutrophils show toxic granulation. Some of the eosinophils are sparsely granulated. Lymphocytes are predominantly small unremarkable forms. Red cells show normochromic normocytic anemia with occasional acanthocytes. Platelets are markedly reduced in accordance with automated counts with variation in size and poor granulation.

Bone marrow biopsy:

Variably cellular core with many patches devoid of cells and others with a cellularity of ~40%. A segment of bone shows bone remodeling, perhaps the site of previous biopsy tract. Hematopoiesis is predominantly comprised of erythropoiesis with markedly reduced granulopoiesis. Numerous foci of early erythroid precursors form large colonies throughout the marrow interstitium. In some foci, the pattern is more infiltrative. These cells morphologically resemble blasts and some are noted to be undergoing karyorrhexis. Late erythroid precursor islands are also appreciated in keeping with maturation. There is a smaller population of immature mononuclear cells distinct from the immature erythroids, suspicious for myeloblasts. Megakaryocytes are normal to focally increased in number with dysplastic features. Many are small and abnormally lobated with some naked nuclei seen. Focal clustering is seen. There is background stromal damage including nuclear debris, eosinophil degranulation and hemosiderin-laden macrophages. Occasional scattered spindle cells are noted throughout the core. Lymphoid and plasma cells are not increased.

Bone marrow aspirate:

The bone marrow aspirate smears show numerous hypercellular spicules.

A 500 cell count differential yields:

Blasts 6%

Promyelocytes 0%

Myelocytes 0%

Metamyelocytes 0%

Bands 0%

Seg 0%

Eos 1%

Baso1%

Lymph 2%

Plasma cell 2%

Monocytes 1%

Erythroid precursors 87%,

M:E = 0.1:1

Blasts account for 6% of total cells and 46% of total non-erythroid cells on the differential cell count. The blasts are intermediate to large in size with irregular nuclear membrane, fine nuclear chromatin, prominent nucleolus, and modest to abundant pale blue cytoplasm. No Auer rods are seen. There is a marked erythroid hyperplasia with numerous left-shifted erythroid precursors and dyserythropoiesis characterized by nuclear irregularities, nuclear bridging, karyorrhexis, and budding. Greater than 10% of the erythroids appear to be differentiated. Cytoplasmic vacuoles are not prominent. Very few granulocytes are identified thus precluding an accurate assessment of dysgranulopoiesis. Megakaryocytes are markedly increased with variation in size and many showing widely-separated nuclei. Small and hypolobated forms are also seen. Mast cells are increased and some are spindled in morphology. Numerous hemosiderin-laden macrophages are seen.

An iron stain was performed on the aspirate smear and shows significantly increased iron stores with >15% ring sideroblasts present.

A reticulin stain shows minimal to focal mild increase in reticulin fibrosis.

A CD34 stain shows expression in 5-10% of total cells. Many of the sinuses are dilated and vascularity is increased. CD117 reveals a similar number of positive cells as the CD34 but with expression seen in some erythroid precursors and scattered spindle cells thought to represent mast cells; however, these cells are negative for mast cell tryptase, CD2 and CD25. MPO and CD235a stains reveal the marked reduction in granulocytes with much of the cellularity comprised of erythroid precursors. E-cadherin is a sensitive and specific stain for pronormoblasts in the bone marrow and shows positivity in the large colonies of immature erythroids. CD68 reveals an increase in histiocytic activity.

Flow cytometric analysis:

Flow cytometry was performed on a portion of the bone marrow aspirate and shows a population of cells in the dim CD45 vs low side scatter region accounting for 8% of total events and with heterogeneous expression of CD34, HLA-DR, CD4 and myelomonocytic antigens. These cells are negative for cMPO and CD117. The erythroid precursors are analyzed separately and show mainly CD36 and CD71 expression with some positivity for CD235a, demonstrating a predominantly immature phenotype.

Cytogenetic analysis was performed on a portion of the aspirate and shows a normal male karyotype in 20 metaphases analyzed.

None

Course:

Induction chemotherapy was not deemed a therapeutic option given the patient’s hepatitis C infection and possibility of viral reinactivation. Hypomethylating agents such as azacytidine were considered but could not be obtained upon request. The patient remained transfusion dependent and, four months later, passed away from numerous complications including sepsis.

Interesting feature(s) of submitted case:

Our case demonstrates a diagnostic dilemma in a patient with a previously diagnosed erythroid predominant myelodysplastic syndrome (MDS-E), RCMD+RS with normal conventional cytogenetics. According to the WHO 2008, for myeloid neoplasms with >50% marrow erythroid elements that are not therapy-related or AML with recurrent cytogenetic abnormalities, the blast count plays a critical role in further classification. The immunophenotypic blast count in this case is difficult to definitively ascertain; however, based on the differential cell count in this study, myeloblasts are less than 20% of total cells and the case cannot be placed in the AML with myelodysplasia-related changes category despite the history of MDS. The percentage of >80% erythroids may suggest a diagnosis of pure erythroid leukemia (PEL); however, the number of myeloblasts as a percentage of total cells is above that usually seen in PEL. In addition, almost all PEL cases carry a high risk, complex karyotype not seen in this case. Karyotype risk group and IPSS karyotype risk grouping appear to be strongly associated with prognosis in both AEL and MDS-E such that perhaps, certain cytogenetic groups may help place cases in a particular category. In these patients, the blast or erythroid counts may not be as critical in the treatment plan as the underlying cytogenetic signature. The lack of a cytogenetic aberration in this case poses challenges for both diagnosis and prognosis of the entity in question.

Lastly, we consider that erythroid hyperproliferations with left-shifted maturation can be seen in non-neoplastic conditions and, thus, reactive non-neoplastic causes to explain the findings need to be excluded, especially given the patient’s history of HCV, possible hemochromatosis and markedly elevated endogenous erythropoietin level. It is unclear why the patient had such an elevated erythropoietin level. Speculations include bone marrow resistance due to defective erythropoietin receptor or excess production by the liver. Due to the striking dyserythropoiesis noted, it was concluded that the primitive erythroid population in this case was neoplastic even in the absence of a karyotypic cytogenetic alteration driving it. Perhaps there are cryptic cytogenetic or molecular abnormalities yet to be discovered with an important role in pathogenesis of entities such as our case.

According to the current WHO classification: Acute erythroleukemia

Proposed diagnosis: Acute myeloid leukemia with myelodysplasia-related changes (AML-MRC), erythroleukemia type

Blasts at the present specimen were CD71-, CD235a-negative. The bone marrow at the time of "refractory anemia with multilineage dysplasia and ring sideroblasts" showed 2-4% blasts, 72% erythroid with dyserythropoiesis, 25% ring sideroblasts, and a normal karyotype.

Progression of erythroid predominant myelodysplastic syndrome to acute erythroid leukemia, erythroid/myeloid versus refractory anemia with excess blasts-1

Case 330