DNA FISH Diagnostic Assay on Cytological Samples of Thyroid Follicular Neoplasms.

Philippe Vielh,Zsofia Balogh,Jean-Michel Bidart,Bernard Caillou,Ludovic Lacroix,Voichita Suciu,Vladimir Lazar,Martin Schlumberger,Jean-Yves Scoazec,Paul Hofman,Adel El-Naggar,Bastien Job,Abir Ghuzlan,Nelly Motte,Catherine Richon,Guillaume Meurice,Alexander Valent,Philippe Dessen,Virginie Marty

doi:10.3390/cancers12092529

Abstract

Simple SummaryCytopathology cannot distinguish benign from malignant follicular lesions in 20–30% of cases. These indeterminate cases includes the so-called follicular neoplasms (FNs) according to The Bethesda System for Reporting Thyroid Cytopathology. Frozen samples from 66 classic follicular adenomas (cFAs) and carcinomas (cFTCs) studied by array-comparative genomic hybridization identified three specific alterations of cFTCs (losses of 1p36.33-35.1 and 22q13.2-13.31, and gain of whole chromosome X) confirmed by fluorescent in situ hybridization (FISH) in a second independent series of 60 touch preparations from frozen samples of cFAs and cFTCs. In a third independent set of 27 cases of already stained pre-operative fine-needle aspiration cytology samples diagnosed as FNs and histologically verified, FISH analysis using these three markers identified half of cFTCs. Specificity of our assay for identifying cFTCs is higher than 98% which might be comparable with BRAF600E testing in cases of suspicion of classic papillary thyroid carcinomas.Although fine-needle aspiration cytology (FNAC) is helpful in determining whether thyroid nodules are benign or malignant, this distinction remains a cytological challenge in follicular neoplasms. Identification of genomic alterations in cytological specimens with direct and routine techniques would therefore have great clinical value. A series of 153 cases consisting of 72 and 81 histopathologically confirmed classic follicular adenomas (cFAs) and classic follicular thyroid carcinomas (cFTCs), respectively, was studied by means of different molecular techniques in three different cohorts of patients (pts). In the first cohort (training set) of 66 pts, three specific alterations characterized by array comparative genomic hybridization (aCGH) were exclusively found in half of cFTCs. These structural abnormalities corresponded to losses of 1p36.33-35.1 and 22q13.2-13.31, and gain of whole chromosome X. The second independent cohort (validation set) of 60 pts confirmed these data on touch preparations of frozen follicular neoplasms by triple DNA fluorescent in situ hybridization using selected commercially available probes. The third cohort, consisting of 27 archived cytological samples from an equal number of pts that had been obtained for preoperative FNAC and morphologically classified as and histologically verified to be follicular neoplasms, confirmed our previous findings and showed the feasibility of the DNA FISH (DNA fluorescent in situ hybridization) assay. All together, these data suggest that our triple DNA FISH diagnostic assay may detect 50% of cFTCs with a specificity higher than 98% and be useful as a low-cost adjunct to cytomorphology to help further classify follicular neoplasms on already routinely stained cytological specimens.

Highlights

Thyroid nodules are a frequent finding, as they are palpable in approximately 5–10% of adults and detectable in 50–70% of people over the age of 60 by means of ultrasonography (US) [1,2,3]
The initial diagnosis of classic follicular thyroid carcinomas (cFTCs) performed on paraffin-embedded histopathological samples according to the 2004 WHO classification [37] was kept
37 (63%) out of 59 classic follicular adenomas (cFAs) and 30 (58%) out of 52 cFTCs (15 of which were unsatisfactory for interpretation) were DNA

Summary

Introduction

Thyroid nodules are a frequent finding, as they are palpable in approximately 5–10% of adults and detectable in 50–70% of people over the age of 60 by means of ultrasonography (US) [1,2,3]. In 70–80% of all cases, FNAC provides a definitive diagnosis of benign lesions or papillary thyroid cancer (PTC) [1]. A meta-analysis published in 2012 reported that cytopathology alone cannot reliably distinguish benign from malignant follicular lesions in 20–30% of cases [13]. Such cases correspond to one of the three following TBSRTC indeterminate categories, the so-called “gray zone”: atypia or follicular lesion of undetermined significance (AUS/FLUS: category III), follicular or suspicious for a follicular neoplasm (FN/SFN: category IV) and suspicious for malignancy

Methods

Results

Conclusion