Role of CDKN2C Fluorescence In Situ Hybridization in the Management of Medullary Thyroid Carcinoma.

Medullary thyroid carcinoma (MTC), an aggressive form of thyroid cancer, occurs sporadically in approximately 75% of MTCs. and mutations play a role in about 40% and 15%, respectively, of sporadic MTCs and are predominant drivers in MTC pathways. These mutations are some of the most comprehensively described and screened for in MTC patients; however, in recent studies, other mutations in the gene (p18) have been implicated in the tumorigenesis of MTC. Comparative genomic hybridization analysis revealed that approximately 40% of sporadic MTC samples have loss of at chromosome 1p32 in addition to frequent losses of (p19) at chromosome 19p13. However, no feasible routine method had been established to detect loss of heterozygosity (LOH) of and The aim of this study is to assess the feasibility of using Fluorescence in situ Hybridization (FISH) to screen MTC patients for and deletions. We subjected 5 formalin-fixed, paraffin-embedded (FFPE) MTC samples with defined RET/RAS mutations to dual-color FISH assays to detect loss of and/or We prepared spectrum orange probes using the bacterial artificial chromosomes RP11-779F9 for (p18) and RP11-177J4 for (p19) and prepared spectrum green control probes to the 1q25.2 and 19q11 regions (RP11-1146A3 and RP11-942P7, respectively). Nine FFPE normal thyroid tissue samples were used to establish the cutoff values for the FISH signal patterns. Of the five FFPE MTC samples, four and one yielded a positive significant result for loss and loss, respectively. The results of a Clinical Laboratory Improvement Amendments validation with a CDKN2C/CKS1B probe set for (p18) loss of heterozygosity were 100% concordant with the FISH results obtained in this study. Thus, FISH is a fast and reliable diagnostic or prognostic indicator of gene loss in MTC.