Genomic profiling of myeloid sarcoma by array comparative genomic hybridization

Myeloid sarcoma (MS) is a tumor mass of myeloblasts or immature myeloid cells occurring in an extramedullary site. In this study, seven cases of MS [stomach (1), testis (1), skin (2), and lymph node (3)] and 3 synchronous and 1 follow-up bone marrow (BM) samples were studied for genomic abnormalities using array comparative genomic hybridization (array-CGH). Array-CGH construction used approximately 5,400 bacterial artificial chromosome clones from the RPCI-11 library, spanning the human genome. Data were analyzed using the DNAcopy software and custom heuristics. All MS cases had genomic abnormalities detected by array-CGH. Unbalanced genomic abnormalities in five MS cases were confirmed by conventional cytogenetics (CC) and/or fluorescence in situ hybridization (FISH); these abnormalities included loss of 4q32.1-q35.2, 6q16.1-q21, and 12p12.2-p13.2 and gain of 8q21.2-q24.3, 8, 11q21-q25, 13q21.32-q34, 19, and 21. Array-CGH was also invaluable in identifying possible deletions, partner translocations, and breakpoints that were questionable by CC. The remaining two MS cases had genomic aberrations detected by array-CGH, but were not studied further by CC/FISH. Chromosome 8 was most commonly abnormal (3/7 cases). Identical genomic abnormalities were demonstrated in MS and in synchronous BM in two cases. These results demonstrate that array-CGH is a powerful tool to screen MS tissue for unbalanced genomic abnormalities, allowing identification of chromosome abnormalities when concurrent BM is nonanalyzable or nonleukemic.