Acute myeloid leukemia (AML) is characterized by the proliferation of leukemic myeloid blasts bearing granules and/or Auer rods. Besides acute promyelocytic leukemia, the myeloid blasts in other subtypes of AML have a non-descript morphology.
The aim of this analysis was to determine the morphological features of t (8;21) positive AML and define a score for predicting positivity for this fusion protein in AML.
A retrospective analysis of all the cases of AML diagnosed over a period of five years (2013-2017) at our centre was performed. The clinical and laboratory data of the patients was collected from the patient medical records. The bone marrow aspirate smears were reviewed to define the specific features of t (8;21) positive AML; dyspoiesis in maturing granulocytes, long thin Auer rods, eosinophilia, cytoplasmic vacuoles and presence of Auer rods in maturing myeloid cells.
A total of 68 cases of t (8;21) positive AML were diagnosed during the study period, with a median age of 19.5 years (range 5-75 years) with a M:F of 1.7:1. Only twenty percent (14/68) patients belonged to the paediatric age-group (≤14 years). Granulocytic sarcoma was observed in 10.2% patients at presentation. Morphologically, in accordance to the FAB classification there were 56 AML-M2, 5 AML-M1 and 7 AML-M4 subtypes. Thirteen cases (n = 68) exhibited less than 20% blast in the bone marrow. Characteristic morphological features included presence of dyspoiesis (71%), slender long Auer rods (48%), eosinophilia (19%) cytoplasmic vacuoles in the golgi zone of blasts and maturing myeloid cells (48%). Mast cells, and Auer rods in maturing granulocytic series of cells were seen in a very small fraction of patients, 11% and 3% respectively. 29/68 patients opting for treatment were managed as per the 3+7 protocol. Seventy percent (21/30) achieved CR; there were 5 induction and 8 post induction deaths. With a median follow-up of 27 months, (range 4-51 months), the overall survival is 40%. Eleven patients relapsed with a median interval of 7 months, twelve patients-maintained CR.
Since this sub-group of AML is believed to be a harbinger of good prognosis, recognition of the distinct morphological features of AML1-ETO AML is essential; it will facilitate a screening for this genetic abnormality. There was no prognostic correlation with any laboratory parameter, however, presence of granulocytic sarcoma in these patients portends a poor prognosis.