3q27

3q27 is a cytogenetic band on the long arm of human chromosome 3, denoting a region at about 3q27. In clinical cytogenetics, abnormalities involving this band are most often discussed in the context of hematologic malignancies. The region encompasses several genes, the most notable being BCL6, which is located at 3q27.3.

BCL6 encodes a zinc finger transcriptional repressor that plays a key role in germinal center B-cell development and differentiation. Deregulation of BCL6, through chromosomal rearrangements, amplifications, or other alterations at 3q27, can contribute to lymphomagenesis by altering transcriptional programs that control B-cell maturation and apoptosis. Among the structural changes observed, translocations involving 3q27 and partner loci are common in certain B-cell lymphomas.

A well-described example is a translocation between 3q27 and 14q32, t(3;14)(q27;q32), which can juxtapose BCL6 next to immunoglobulin heavy chain enhancers and lead to BCL6 overexpression. Such rearrangements have been detected in diffuse large B-cell lymphoma and related B-cell neoplasms. In addition to rearrangements, copy number changes at 3q27, including amplifications, have been reported in hematologic malignancies and occasionally in solid tumors, though their biological impact varies by context.

Detection of 3q27 abnormalities is typically accomplished through conventional karyotyping and fluorescence in situ hybridization (FISH) using BCL6-specific probes, as well as chromosomal microarray for copy number changes. Understanding alterations at 3q27 helps in the molecular characterization and, in some cases, the diagnostic classification of lymphoid neoplasms.