Abstract

Mycosis fungoides (MF) is the commonest cutaneous lymphoma. While copy number variation (CNV) has been studied extensively in other tumors such as melanoma, significantly less research has been done on CNVs in MF. The limited data on this topic has generally been obtained with array-based technologies such as array Comparative Genomic Hybridization (aCGH), which reveals evidence for CNVs in various loci. We reviewed cases of advanced MF from archival material spanning 2016 to 2021. Densely inflamed lichenoid dermatidites were also retrieved and used as controls. In this pilot study, Fluorescence In Situ Hybridization (FISH) for the CDKN2A loci and CEP9 centromeric loci was performed. Over 1600 hybridizations, from 400 nuclei, across 8 initial cases, were manually counted. Four cases were MF, while the remaining 4 were from inflammatory skin. The distribution of CDKN2A DNA probe hybridizations differed between lymphoma and control groups; the difference was statistically significant, with a corresponding p value of 0.046. The distributions of the CEP9 loci between the two groups did not differ. Notably, the FISH studies uncovered a hitherto undocumented phenomenon: a subpopulation of cells in advanced MF with copy number gain of CDKN2A. Deletion of CDKN2A locus is commonplace in many tumors. Copy number gain of this locus is rare, but has been documented in other cancers. We report these findings for the first time, discuss their implications, and offer suggestions for larger follow-up studies to investigate further use of FISH in MF.

Financial Disclosure: No current or relevant financial relationships exist.