Endocrine Abstracts

Background: Follicular differentiated thyroid cancer (FDTC) is the most common endocrine cancer, globally. Next-generation sequencing (NGS) in thyroid cancer allows for high-throughput genetic sequencing in short time. This analysis offers useful information on tumor biology. NGS Studies on follicular differentiated thyroid cancer are scanty from South East Asia. In this context, we set out study the pattern of a genetic panel wide somatic mutations in thyroid cancer.

Methods: We selected 20 FDTC cases. All of them underwent total thyroidectomy with neck dissection as needed. Tumour tissue samples extracted and paraffin embedded, were taken from ex-vivo specimen. Sample processing, DNA extraction, cDNA preparation and PCR amplification was performed. Mutation analysis with a thyroid cellular pathway specific 56-gene mutation panel using real-time PCR and ThyroSeq v2 on the Ion Torrent PGM sequencer was employed. Common single nucleotide polymorphisms (SNPs) with a minor allele frequency of >0.05 were excluded. Mutations were also manually checked using the Integrated Genomics Viewer v2.4.10 to filter out false positives.

Results: The analysis found mutations commonly in BRAF (16), CDKN2A (10), NRAS (6), PI3KCA (9), RET (4), RAS (12) and TP53 (3) genes. The common mutations found in the samples was RET (M918T), NRAS (Q61R), BRAF (V600E) and missense mutation in TP53 (c.217 – c.1178). A mutation has also been identified in KMT2D gene in two of the patient samples. BRAF, CDKN2A, PI3KCA were more common in papillary cancer. RAS, NRAS, RET mutations were common in follicular cancer. TP53 and KMT2D were seen only in poorly differentiated cancer.

Conclusions: NGS helps in patient management, providing risk stratification and subtyping of malignancy. It can be used in molecular tumor classification, and molecular prediction of long term outcomes in thyroid carcinoma. More prospective studies are needed for its routine use at clinical level.

Keywords: Thyroid cancer; BRAF gene; RAS gene; Genomics; Mutation