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Eur J Endocrinol. 2015 May;172(5):571-82. doi: 10.1530/EJE-14-0930. Epub 2015 Feb 19.

Break-apart interphase fluorescence in situ hybridization assay in papillary thyroid carcinoma: on the road to optimizing the cut-off level for RET/PTC rearrangements.

Author information

1
Department of Pathology and DiagnosticsARC-NET Research CentreUniversity of Verona, Policlinico GB Rossi, Piazzale LA Scuro, 10, Piastra Odontoiatrica (II floor), 37134 Verona, ItalyDepartment of Internal MedicineEndocrinology, and Metabolism and Biochemistry, University of Siena, Siena, ItalyDepartment of Surgery and OncologyUniversity of Verona, Verona, ItalyDivision of SurgicalMolecular and Ultrastructural, Section of Cytopathology, University Hospital of Pisa, Pisa, ItalyNuclear Medicine UnitUniversity Hospital of Verona, Verona, Italy chiara.colato@ospedaleuniverona.it.
2
Department of Pathology and DiagnosticsARC-NET Research CentreUniversity of Verona, Policlinico GB Rossi, Piazzale LA Scuro, 10, Piastra Odontoiatrica (II floor), 37134 Verona, ItalyDepartment of Internal MedicineEndocrinology, and Metabolism and Biochemistry, University of Siena, Siena, ItalyDepartment of Surgery and OncologyUniversity of Verona, Verona, ItalyDivision of SurgicalMolecular and Ultrastructural, Section of Cytopathology, University Hospital of Pisa, Pisa, ItalyNuclear Medicine UnitUniversity Hospital of Verona, Verona, Italy.
3
Department of Pathology and DiagnosticsARC-NET Research CentreUniversity of Verona, Policlinico GB Rossi, Piazzale LA Scuro, 10, Piastra Odontoiatrica (II floor), 37134 Verona, ItalyDepartment of Internal MedicineEndocrinology, and Metabolism and Biochemistry, University of Siena, Siena, ItalyDepartment of Surgery and OncologyUniversity of Verona, Verona, ItalyDivision of SurgicalMolecular and Ultrastructural, Section of Cytopathology, University Hospital of Pisa, Pisa, ItalyNuclear Medicine UnitUniversity Hospital of Verona, Verona, Italy Department of Pathology and DiagnosticsARC-NET Research CentreUniversity of Verona, Policlinico GB Rossi, Piazzale LA Scuro, 10, Piastra Odontoiatrica (II floor), 37134 Verona, ItalyDepartment of Internal MedicineEndocrinology, and Metabolism and Biochemistry, University of Siena, Siena, ItalyDepartment of Surgery and OncologyUniversity of Verona, Verona, ItalyDivision of SurgicalMolecular and Ultrastructural, Section of Cytopathology, University Hospital of Pisa, Pisa, ItalyNuclear Medicine UnitUniversity Hospital of Verona, Verona, Italy.

Abstract

OBJECTIVE:

Chromosomal rearrangements of the RET proto-oncogene is one of the most common molecular events in papillary thyroid carcinoma (PTC). However, their pathogenic role and clinical significance are still debated. This study aimed to investigate the prevalence of RET/PTC rearrangement in a cohort of BRAF WT PTCs by fluorescence in situ hybridization (FISH) and to search a reliable cut-off level in order to distinguish clonal or non-clonal RET changes.

DESIGN:

Forty BRAF WT PTCs were analyzed by FISH for RET rearrangements. As controls, six BRAFV600E mutated PTCs, 13 follicular adenomas (FA), and ten normal thyroid parenchyma were also analyzed.

METHODS:

We performed FISH analysis on formalin-fixed, paraffin-embedded tissue using a commercially available RET break-apart probe. A cut-off level equivalent to 10.2% of aberrant cells was accepted as significant. To validate FISH results, we analyzed the study cohort by qRT-PCR.

RESULTS:

Split RET signals above the cut-off level were observed in 25% (10/40) of PTCs, harboring a percentage of positive cells ranging from 12 to 50%, and in one spontaneous FA (1/13, 7.7%). Overall, the data obtained by FISH matched well with qRT-PCR results. Challenging findings were observed in five cases showing a frequency of rearrangement very close to the cut-off.

CONCLUSIONS:

FISH approach represents a powerful tool to estimate the ratio between broken and non-broken RET tumor cells. Establishing a precise FISH cut-off may be useful in the interpretation of the presence of RET rearrangement, primarily when this strategy is used for cytological evaluation or for targeted therapy.

PMID:
25698220
DOI:
10.1530/EJE-14-0930
[Indexed for MEDLINE]

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