Impact of ultrasonographic features, cytomorphology and mutational testing on malignant and indeterminate thyroid nodules on diagnostic accuracy of fine needle cytology samples: A prospective analysis of 141 patients

Abstract

Objective: Fine needle cytology (FNC) is the first-line diagnostic method to determine the benign or malignant nature of thyroid nodules. The gray zone of cytological classifications remains, however, a crucial and challenging area for cytopathologists.

Design, patients and measurements: In the present study, 141 thyroid cytological samples, with ultrasonographic suspicious features, have been prospectively analysed. Molecular analyses were performed by an innovative technology using two multiplex PCRs for the amplification of BRAF, N-H-K-RAS and RET exon genes. RNA samples were studied for RET/PTC1 and RET/PTC3 rearrangements by PCR amplification, and the conditions were set-up to study, with a single experiment, both wild-type PAX8 and PAX8/PPARɣ rearrangements. In total, 111 samples were examined for BRAF, N-H-KRAS and RET genes. An ultrasonographic, cytological and molecular correlation was also carried out in an attempt to suggest a possible way to manage the patients with thyroid nodules. Cyto-histological correlation was available in 115 cases, and it was used to verify the global diagnostic accuracy of this combined approach.

Results: According to the histopathological diagnosis, FNC accuracy was 100% for TIR5 and metastases; 89% for TIR4; 84% for TIR3A and 58% for TIR3B. About 11% of the studied samples showed either RET-PTC1 or RET/PTC3 chromosomal rearrangements, and only one sample simultaneously presented RET/PTC1 and RET/PTC3 rearrangements. PAX8/PPARɣ rearrangement was found in 6% of the samples.

Conclusions: A multidisciplinary approach to the thyroid is therefore necessary to develop innovative methods suitable for an improved diagnostic and prognostic definition of thyroid cancer.

Keywords: cyto-histological correlation; fine needle cytology; indeterminate nodules; mutational analysis; papillary thyroid carcinoma; thyroid cancer treatment; ultrasound features.

Figure 1

A, BRAF‐RAS multiplex amplification gel, genes are indicated. B, RET multiplex amplification gel, RET exons are reported. C, Multiplex PAX8 wild‐type and PAX8/PPARɣ rearrangement samples amplification, PAX8 wild‐type and PAX8/PPARɣ rearrangements size are reported. Amplifications of two samples (121 and 99), a positive control (Cwt + Cr) and a negative control (C−). Samples 99 was negative for PAX8 wild‐type amplification and positive for PAX8/PPARɣ rearrangement

Figure 2

Flow chart showing the molecular status and histopathological diagnoses of cases cytologically defined as TIR3A/B, TIR4 and TIR5 on EU‐TIRADS ultrasound classification

Figure 3

Flow chart showing the proposed treatment of thyroid nodules according to EU‐TIRADS ultrasound classification, cytological diagnosis and mutational status