Putative natural killer (NK) cell lymphoma/leukemia is a rare group of recently characterized hematolymphoid malignancies. They are highly aggressive and frequently present in extranodal sites, including the nasal area and the upper aerodigestive system, and nonnasal areas such as the skin and the gastrointestinal tract. According to clinicopathological features, they can be classified into nasal NK cell lymphoma, nasal-type NK cell lymphoma occurring in nonnasal areas, and NK cell lymphoma/leukemia. Genetic alterations in NK cell lymphoma/leukemia are not well defined. In this study, we have performed comparative genomic hybridization (CGH) on DNA extracted from fresh or frozen tissues of 10 patients with NK cell lymphoma/leukemia. They comprised four nasal NK cell lymphomas, one nasal-type NK cell lymphoma, and five NK cell lymphomas/leukemias. CGH showed frequent deletions at 6q16-q27 (four cases), 13q14-q34 (three cases), 11q22-q25 (two cases), 17p13 (two cases), and loss of the whole chromosome X (two cases). DNA amplification was observed in a majority of the chromosomes. Five cases showed DNA gains at region 1p32-pter. Frequent DNA gains were also found in chromosomes 6p, 11q, 12q, 17q, 19p, 20q, and Xp (three cases each). Interestingly, DNA gains were more frequent in nasal/nasal-type NK cell lymphomas than NK cell lymphoma/leukemia. These genetic alterations correlated well with karyotypic features found in some of the cases. The frequent DNA losses at 6q and 13q suggest that the presence of tumor suppressor genes at these regions is important in NK cell transformation. In addition to establishing novel patterns of genomic imbalances in these rare NK cell malignancies, which may be targets for future molecular analysis, this study also provides important information on genetic alterations in NK cell lymphomas that may be useful in defining their positions in current lymphoma classification schemes, which are increasingly focusing on phenotypic and genotypic correlations.

Natural killer (NK) cell lymphomas are a group of rare but highly aggressive malignancies. Clinically, they can be divided into nasal NK cell lymphomas, nonnasal NK cell lymphomas, and aggressive NK cell lymphoma/leukemia. To determine the patterns of genetic deletions in these tumors, we performed loss of heterozygosity (LOH) analysis on 15 cases (11 nasal and four nonnasal), and fluorescence in situ hybridization on three cases of aggressive lymphoma/leukemia. A panel of 41 microsatellite loci on chromosomes 6q, 11q, 13q, and 17p were investigated. LOH at chromosomes 6q and 13q was frequently detected in NK cell lymphomas, being found in 80 and 66.7% of cases, respectively. LOH at chromosomes 11q and 17p was less common, being found in 28.6 and 30.8% of cases, respectively. Most tumors showed multiple loci deletions at different chromosomal regions, but several patterns of LOH could be defined. LOH at chromosome 6q was found in 90.9% of nasal NK cell lymphomas, but only in 50% of nonnasal NK cell lymphomas. LOH at chromosome 13q was found in 63.6% of nasal NK cell lymphomas and 75% of nonnasal NK cell lymphomas. For nasal NK cell lymphomas, LOH at 13q was found in 33.3% of cases at presentation, but 100% of cases at relapse. Five tumors showed LOH in only one chromosomal region, involving 6q in three cases (two nasal and one nonnasal), and 13q in two cases (both nonnasal). For the three cases of aggressive NK cell lymphoma/leukemia studied by fluorescence in situ hybridization, DNA loss at 13q14 and 17p13 regions were demonstrated. 17p13 seemed to be more commonly involved in aggressive than nasal and nonnasal NK cell lymphomas. Our results suggested that consistent patterns of LOH could be defined in NK cell malignancies. These deleted loci may contain genes important in the initiation and progression of this lymphoma.

Summary. Natural killer (NK) cell lymphomas lack suitable clonal markers for tumour cell detection, making the monitoring of minimal residual lymphoma difficult. Aberrant promoter CpG methylation occurs frequently in NK cell lymphomas. The objective of this study was to assess the potential of aberrant methylation as a surrogate tumour marker. Twenty-five primary tumours and 105 serial biopsies taken at various time points after treatment were examined using a methylation-specific polymerase chain reaction (MSP) for a panel of genes, comprising p73, p16, hMLH1, RARb and p15, previously shown to be methylated in NK cell lymphomas. All samples underwent independent morphological examination, supplemented by immunostaining for CD56 and in-situ hybridization for Epstein-Barrvirus-encoded RNA. Primary tumours showed the frequent methylation of the genes p73 (92%), p16 (71%), hMLH1 (61%), RARb (56%) and p15 (48%). MSP results in serial post-treatment biopsies were correlated with clinicopathological findings. Results were concordant in 89 follow-up samples (18 samples, histology positive/MSP positive; 71 samples, histology negative/MSP negative) and discordant in 16. Fifteen samples were histology negative/MSP positive, and tumour involvement was subsequently confirmed (positive re-biopsies or relapses at the same sites), indicating that MSP was more sensitive for minimal lymphoma detection. One sample was histology positive/MSP negative; a subsequent histological review and continuous clinical remission of the patient did not support tumour involvement. Our findings suggest that MSP for aberrantly methylated genes is a potentially valuable molecular marker for detecting either residual or relapsed disease in NK cell lymphoma patients.

Clinical outcome and mutations of 96 core-binding factor acute myeloid leukemia (AML) patients 18–60 years old were examined. Complete remission (CR) after induction was 94.6%. There was no significant difference in CR, leukemia-free-survival (LFS) and overall survival (OS) between t(8;21) (N=67) and inv(16) patients (N=29). Univariate analysis showed hematopoietic stem cell transplantation at CR1 as the only clinical parameter associated with superior LFS. Next-generation sequencing based on a myeloid gene panel was performed in 72 patients. Mutations in genes involved in cell signaling were associated with inferior LFS and OS, whereas those in genes involved in DNA methylation were associated with inferior LFS. KIT activation loop (AL) mutations occurred in 25 patients, and were associated with inferior LFS (P=0.003) and OS (P=0.001). TET2 mutations occurred in 8 patients, and were associated with significantly shorter LFS (P=0.015) but not OS. Patients negative for KIT-AL and TET2 mutations (N=41) had significantly better LFS (P<0.001) and OS (P=0.012) than those positive for both or either mutation. Multivariate analysis showed that KIT-AL and TET2 mutations were associated with inferior LFS, whereas age ⩾40 years and marrow blast ⩾70% were associated with inferior OS. These observations provide new insights that may guide better treatment for this AML subtype.