Sole Infrequent Karyotypic Aberration Trisomy 6 in a Patient with Acute Myeloid Leukemia and Breast Cancer in Remission

TO THE EDITOR,

Cytogenetic abnormalities play important roles in the diagnosis and prognosis of leukemias [1]. Trisomy 6 as the sole karyotypic aberration is infrequent in leukemias [1,2]. A 50-year-old female patient presented with fatigue. She had been treated by mastectomy and given chemotherapy (no further information available) for breast cancer 3 years ago. She had been using tamoxifen for 3 years. Her breast cancer was in remission. Physical examination was consistent with a pale appearance. Hemoglobin, neutrophils, and platelet count were 8.5 g/dL, 900/µL, and 11,000/µL, respectively, on admission. In the peripheral blood smear, there were dysplastic features in monocytes and a few blasts were reported. In flow cytometry, CD13, CD33, CD34, CD45, CD117 (c-kit), HLA-DR, and MPO were positive. Bone marrow aspiration and biopsy revealed hypercellularity with dysplastic and megaloblastic features in erythroid series, grade 1/3 reticulin fibrosis, and 24% blasts without ring sideroblasts, which in turn with cytometry findings were accepted as evidence of acute myeloid leukemia (AML). Bone marrow cytogenetic analysis revealed trisomy 6 (47,XX, +6 [20]) in all the metaphases (Figure 1). The patient was not in remission after the first induction treatment and she passed away due to septic shock during the second induction treatment.

Figure 1. Bone marrow cytogenetic analysis revealed trisomy 6 (47,XX, +6 [20]) in all the metaphases.

Chromosome aberrations detected in therapy-related AML (t-AML) and de novo AML cases are identical but their frequencies may differ [3]. In a series at the University of Chicago, normal karyotypes were seen in 9.6% of t-AML cases [4]. In the report of Godley and Larson, among 306 patients with t-AML, 32 had solid breast cancer as the primary diagnosis [5]. Alkylating exposures and topoisomerase II inhibitors are associated with t-AML [3,6]. Godley and Larson mentioned granulocyte colony-stimulating factor usage as a risk factor in t-AML after breast cancer [5]. Unfortunately, we do not know which agents were given for our patient’s breast cancer.

Autosomal trisomies have been described in several hematologic malignancy cases. The first case of sole trisomy 6 was reported in aplastic anemia. Other reports showed that trisomy 6 was associated with hypoplastic bone marrow, dyserythropoiesis, and AML [7]. Mohamed et al. reviewed 7 patients with trisomy 6. Patients presenting with overt AML had hyperplastic marrows [8]. Our patient had hypercellular marrow, as well. Mohamed et al. also reviewed the literature and found 4 MDS cases among 22 patients with trisomy 6 [8]. The marrow examination of this case revealed secondary dysplastic leukemia. The patient of Gupta et al. had de novo AML and did not respond to the first remission induction treatment [1].

Yu et al. reviewed ten reports in PubMed describing 18 cases of AML presenting with trisomy 6 as the sole karyotypic abnormality along with 3 cases of their own [7]. They concluded that there were no direct correlations between the number of blasts and the percentage of abnormal metaphases. They could not identify any correlation between morphology or prognosis and trisomy 6 [7].

Under these circumstances, as in our case, we lack information on the impact of trisomy 6 on prognosis in secondary AML patients.