Corpi Auer multipli în blaști și neutrofile la un pacient cu leucemie acută mieloidă nonpromielocitară

A 68-year-old male patient presented in the emergency department complaining of generalized weakness and fatigue with recent onset.

The physical exam revealed pallor, ecchymosis and tachycardia, without organomegaly. Automatic complete blood count (CBC) indicated leukocytosis (95x10⁹/L) with monocytosis (90.2x10⁹/L), mild anemia (hemoglobin 9.9 g/dL) and severe thrombocytopenia (18x10⁹/L).

At coagulation studies, a prolongation of activated partial thromboplastin time and prothrombin time was noticed, together with a normal fibrinogen level. Peripheral blood smear examination showed a polymorphic population of blasts (80% in the white blood cell differential), including large cells with monocytoid or bilobed nucleus, as well as typical myeloblasts.

A subset of blast cells displayed isolated or multiple Auer rods in the cytoplasm. Interestingly, multiple Auer rods were also seen in neutrophils.

Concurrent bone marrow aspirate exam indicated an infiltrate of 70% blast cells that were morphologically similar to those observed in the peripheral blood (Figure 1).

Representative microscopic images (100x magnification) of peripheral blood (A, B, C) and bone marrow aspirate smears (D) showing blast cells with folded monocytoid or bilobed nuclei (A, B, D), along with typical myeloblasts (C); multiple Auer rods are seen in some blasts (B, D – red arrow) and neutrophils (A, C – green arrow)

A high suspicion of acute promyelocytic leukemia (APL), based on morphological exam and abnormal coagulation tests, was raised, and the treatment with all-trans-retinoic acid (ATRA) was initiated.

Next day, flow cytometry analysis performed in the bone marrow aspirate revealed 48% precursor cells with the following phenotype: CD34+/-, CD117+, HLA-DR+, cMPO+, CD33+, CD13+, CD64-/+, CD36+/-, CD14-, CD11b-, cCD79a-, cCD3-, CD3-, CD7-, CD19-, CD56+/-CD9+, CD123+, CD71-, being suggestive for atypical promyelocytes, with aberrant expression of HLA-DR.

However, reverse-transcription PCR did not detect the PML::RARA fusion transcript, instead CBF::MYH11 fusion was identified. No FLT3-ITD and NPM1 mutations were detected at molecular testing using DNA fragment analysis.

According to the 2022 World Health Organization classification of myeloid neoplasms⁽¹⁾, the final diagnosis was acute myeloid leukemia (AML) with CBF::MYH11 fusion. ATRA was discontinued, and the therapy with azacytidine and venetoclax was initiated.

Although the presence of blasts with multiple Auer rods (faggot cells) is considered a hallmark of APL, it has been sporadically described in AML with core-binding factor (CBF) rearrangements.

Except for APL during ATRA treatment, neutrophils with bundles of Auer rods are even a rarer finding, being reported in a few cases of AML with CBF::MYH11 fusion^(2,3).

This work is permanently accessible online free of charge and published under the CC-BY.

Corresponding author: Ana-Maria Vlădăreanu E-mail: anamariavladareanu@yahoo.com

Conflict of interests: none declared.

Financial support: none declared.