AML-MRC with Basophilia Mimicking CLPD Due to Abnormally Clumped Chromatin

Excerpt

A 49-year-old man sought medical attention with a 1-month history of fatigue and intermittent fever. He manifested no hepatosplenomegaly and no lymph node enlargement. Laboratory studies were remarkable for leukocytosis, anemia and thrombocytosis (white blood cells 110 × 10⁹/L, hemoglobin 73 g/L, platelets 636 × 10⁹/L, basophils 4.8 × 10⁹/L) Peripheral blood smears showed 80% mononuclear cells with abnormally clumped nuclear chromatin without prominent nucleoli, alongwith increased mature basophils. (Fig. 1a–d). Bone marrow smears revealed large amounts of mononuclear cells infiltration mimicking mature lymphocytes with abnormally clumped chromatin, basophilia and megakaryocyte dysplasia, which was characterized by the presence of micromegakaryocytes, megakaryocytes with small round nuclei and multiple round nuclei (Fig. 1e–h). Peripheral blood and bone marrow smears were re-stained to avoid the influence of improper dyeing and the result was the same as before. Flow cytometry using CD45 vs SSC gating strategy revealed an abnormal blast population and basophilia. The blast population was positive for CD13, CD33, CD34, CD36, HLA-DR, CD117 and MPO. The basophils were positive for CD123 and CD11b, the blasts being negative for these markers. Besides, the basophils were positive for HLA-DR(Fig. 2). The patient had no prior history of chronic myeloid leukemia, and his BCR/ABL fusion gene was negative using RT-PCR method. Cytogenetic analysis of the BM cells indicated a 46,XY,t(4;12)(q12;p13)[20] karyotype. Due to the high ratio of blood and marrow blasts and dysplasia of myeloid and megakaryocyte, the patient was diagnosed with acute myeloid leukaemia with myelodysplasia related changes (AML-MRC) according to WHO classification [1-2]. The patient received treatment with DA (daunorubicin and cytarabine) protocol after the diagnosis was rendered, and achieved complete remission (CR) after 2 cycles of chemotherapy.

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