Tetraploid clone characterized by two t(15;17) in five cases of acute promyelocytic leukemia

Tetraploid acute promyelocytic leukemia with double translocation t (15,17) PML/RARA: the first case report in Croatia and Europe

Acute promyelocytic leukemia (APL) is characterized by the translocation t (15;17)(q22;q21) cytogenetic abnormality in the majority of cases. In most of the cases the cells of APL have normal, diploid karyotype. There are very few cases presented with very rare tetraploid karyotype with double translocation t(15;17)(q22;q12). We report the first case of tetraploid APL with double translocation t(15, 17) in Europe. A 66-year old male patient presented with dyspnea and unexplained dental bleeding. Blood work showed a white blood cell count of 1x109/L, hemoglobin was 124 g/ L, platelet count was 61x109/L and fibrinogen level was low (1.4 g/L). Cytogenetics showed a tetraploid karyotype. Fluorescence in situ hybridization analysis proved existence of clonal cells with translocation t (15,17) in 15% of metaphase nuclei and tetraploid subclonal cells with the same translocation in 70% of metaphase nuclei. Findings were consistent with APL, tetraploid variant and the patient started all-trans retinoic acid (ATRA) treatment. The patient achieved complete remission in 2 months and completed three consolidation therapy cycles with ATRA, idarubicin or mitraxontrate. Currently, the patient is undergoing maintenance therapy with ATRA, 6-mercaptopurine and weekly methotrexate.

Mitotic recombination of chromosome arm 17q as a cause of loss of heterozygosity of NF1 in neurofibromatosis type 1-associated glomus tumors

Neurofibromatosis type 1 (NF1) is a common, autosomal dominant, tumor-predisposition syndrome that arises secondary to mutations in NF1. Glomus tumors are painful benign tumors that originate from the glomus body in the fingers and toes due to biallelic inactivation of NF1. We karyotyped cultures from four previously reported and one new glomus tumor and hybridized tumor (and matching germline) DNA on Illumina HumanOmni1-Quad SNP arrays (≈ 1 × 10(6) SNPs). Two tumors displayed evidence of copy-neutral loss of heterozygosity of chromosome arm 17q not observed in the germline sample, consistent with a mitotic recombination event. One of these two tumors, NF1-G12, featured extreme polyploidy (near-tetraploidy, near-hexaploidy, or near-septaploidy) across all chromosomes. In the remaining four tumors, there were few cytogenetic abnormalities observed, and copy-number analysis was consistent with diploidy in all chromosomes. This is the first study of glomus tumors cytogenetics, to our knowledge, and the first to report biallelic inactivation of NF1 secondary to mitotic recombination of chromosome arm 17q in multiple NF1-associated glomus tumors. We have observed mitotic recombination in 22% of molecularly characterized NF1-associated glomus tumors, suggesting that it is a not uncommon mechanism in the reduction to homozygosity of the NF1 germline mutation in these tumors. In tumor NF1-G12, we hypothesize that mitotic recombination also "unmasked" (reduced to homozygosity) a hypomorphic germline allele in a gene on chromosome arm 17q associated with chromosomal instability, resulting in the extreme polyploidy.

Unusually long survival of a 67-year-old patient with near-tetraploid acute myeloid leukemia m0 without erythroblastic and megakaryocytic dysplasia

Patients with near-tetraploid acute myeloid leukemia (NT-AML) typically have poor survival. We present the case of a 67-year-old Caucasian male with NT-AML M0 who had an unusually long first complete remission of 51 months and an overall survival of 80 months. The only characteristic distinguishing him from other previously described patients with NT-AML was the absence of erythroblastic and/or megakaryocytic dysplasia (EMD) at diagnosis. Molecular-genetic testing for AML fusion transcripts associated with a favorable prognosis (PML/RARα,AML1/ETO, and CBFβ/MYH11) were negative, as were other prognostic markers like MLL-PTD,FLT3-ITD, or mutations of FLT3-D835,NPM1, or CEBPA. Expression studies of ERG,MN1, and EVI1 revealed overexpression of ERG only. The absence of EMD may be a useful prognostic/diagnostic feature of this new rare subtype of NT-AML.