Genomic Alterations in Blastic Natural Killer/Extranodal Natural Killer-Like T Cell Lymphoma with Cutaneous Involvement

Natural killer and natural killer-like T cell lymphomas represent a rare type of non-Hodgkin's lymphoma originally described to involve the upper aerodigestive tract. This malignancy has been increasingly observed in other extranodal sites, particularly in the skin. Patients with cutaneous natural killer cell lymphoma generally have a poor prognosis; however, the etiology and the underlying molecular pathogenesis remain unclear. This study aimed to investigate comprehensively genomic changes in blastic natural killer and extranodal natural killer-like T cell lymphoma with cutaneous involvement. Comparative genomic hybridization showed chromosome imbalances in six of eight cases studied (75%). The mean number of chromosome imbalances per sample was 2.18±1.63 with similar number of gains (1.18±1.17) and losses (1.00±1.34). The most frequent DNA copy number changes observed were losses of 9/9p (83%), followed by loss of 13q and gain of 7 (67%). Similar patterns of chromosome imbalances were observed in both blastic natural killer and cutaneous natural killer-like T cell lymphomas. Loss of the RB1 gene at 13q14.2 was detected in one blastic natural killer cell lymphoma with 13q loss using a gene dosage assay, and in one cutaneous natural killer-like T cell lymphoma without 13q loss using fluorescent in situ hybridization. Genomic microarray analysis identified oncogene copy number gains of PAK1 and JUNB in three of four cases studied, and gains of RAF1, CTSB, FGFR1, and BCR in two cases. Real-time polymerase chain reaction detected amplification of CTSB and RAF1 in four of five cases analyzed, JUNB and MYCN in three cases, and REL and YES1 in two cases, respectively. In conjunction with this study, an extensive literature search for the published G-banded karyotypes of four subsets of natural killer cell lymphomas was conducted, which showed a nonrandom pattern of multiple chromosome aberrations. These results reveal consistent genetic alterations in cutaneous natural killer cell lymphomas, and provide a basis for further investigation of molecular pathogenesis in this malignancy