Introduction: Fine-needle aspiration cytology (FNAC) is the primary means to distinguish benign from malignant thyroid nodules. However, adjunctive diagnostic tests are needed as 20-40% of FNAC are inconclusive. RAS mutations have been described in differentiated thyroid cancer and they could be used as tumor markers. However, their prevalence varies widely among studies, probably as a result of the detection methods used. We investigated whether the pyrosequencing method can be applied to detect NRAS and KRAS mutations in thyroid aspirates.
Patients and methods: A total of 37 thyroid aspirates, including benign hyperplastic nodules (HBN, N = 16) and follicular thyroid carcinomas (FTC, N = 21) were analyzed for the presence of NRAS(61) and KRAS(13) mutations.
Results: A RAS mutation was found in 31% and 62% of BN and FTC respectively. Most samples displayed a percentage of mutated alleles lower than 50% (median = 30.8% and 15.3% in FTC and HBN respectively), a result compatible with the presence of extra-nodular cells contaminating the FNA or with the subclonal nature of both types of thyroid nodules.
Discussion: Pyrosequencing is a reliable assay to detect RAS mutations in fine-needle thyroid aspirates.
Conclusions: The low specificity and sensitivity limit the power of this test to distinguish between FTC and benign nodules in inconclusive FNACs.
Keywords: FNAC; RAS; Thyroid carcinoma.
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