Clinico- and Pathogenomic Analyses of a Single Institution Diffuse Large B-Cell Lymphoma Cohort

Abstract

Chromosomal microarray (CMA) is widely used to detect and refine chromosome abnormalities in both congenital and neoplastic cases. Recently, a blood sample from a newborn male with no apparent dysmorphic features was sent to the Mayo Clinic Cytogenetics laboratory for G-banded karyotype analysis to clarify prenatal findings of a positive trisomy 21 noninvasive prenatal screening (NIPS) result. Chromosome analysis of 20 metaphases revealed 13 were normal (46,XY) and 7 had a satellited supernumerary marker chromosome (47,XY,+mar). To further characterize the marker chromosome, CMA studies were performed, which revealed an 8.6 megabase mosaic duplication from 21q11.2 to 21q21.1. Subsequent metaphase FISH studies demonstrated that the duplicated region was present on the supernumerary marker chromosome, indicating that the marker chromosome is derived from chromosome 21. Interphase FISH studies showed that the marker was present in 68% of interphase nuclei. Despite its large size, the duplicated region contains only 30 known genes. In addition, similar duplications involving this region have not been previously described, making the clinical significance of this duplication uncertain. Importantly, the duplicated interval does not include the Down syndrome critical region (21q22.1 to 22q22.3), consistent with this patient’s lack of dysmorphic features. This report highlights the importance of diagnostic follow-up testing and the clinical utility of conventional and molecular cytogenetic techniques in the setting of abnormal NIPS results.