13q142

13q142 is not a standard cytogenetic designation; it most likely refers to the 13q14.2 region on the long arm of chromosome 13. The RB1 gene, a key tumor suppressor, is located at 13q14.2 and is the best-known element of this region. Inactivation of RB1 by mutation or deletion leads to retinoblastoma, a malignant eye tumor that typically occurs in children. Hereditary RB1 mutations can be germline, predisposing to bilateral disease and increasing the risk of additional primary cancers. The development of RB1-related tumors follows the two-hit hypothesis, in which a first hit (germline or somatic) is complemented by a second somatic event in retinal cells.

Beyond RB1, abnormalities involving 13q14 are also observed in other cancers. In chronic lymphocytic leukemia (CLL), larger deletions of 13q (often described as 13q14.3) are common and frequently encompass noncoding RNAs such as DLEU2 and the microRNA cluster miR-15a/16-1. Loss of these miRNAs can disrupt regulation of apoptosis and cell survival, influencing disease biology and response to treatment, including effects on BCL2.

Detection and terminology: standard testing uses G-banding karyotyping and fluorescence in situ hybridization (FISH) with RB1 or 13q14 probes. More comprehensive methods, such as array comparative genomic hybridization (array CGH) and next-generation sequencing, can identify submicroscopic deletions or mutations within this region.

Notes: 13q14.2 is among the most studied loci in cancer genetics due to RB1. In CLL, isolated 13q losses are typically associated with a relatively favorable prognosis compared with other chromosomal abnormalities, though prognosis is context-dependent and influenced by coexisting changes.