Molecular Pathology Laboratory Network

Thyroid molecular analysis is largely limited to fine needle aspirate (FNA) samples; and approximately 10 to 40% of thyroid FNAs are cytologically indeterminate and contribute to a high rate of surgery for benign lesions.

 

Among cytologic follicular lesions of uncertain significance, a mutation or rearrangement in the BRAF, RAS, RET/PTC or PAX8/PPAR gene was found in 100% of confirmed malignant nodules, while uniformly negative results were found in less than 92% of benign nodules - corresponding to a 100% positive predictive value and 92% negative predictive value. In contrast, molecular testing is less often indicated for tumor resections. PAX8/PPAR testing can help distinguish resected minimally invasive follicular carcinoma from follicular adenoma. Experts agree that molecular testing for BRAF, RAS, RET/PTC and PAX8/PPAR can be considered for indeterminate FNA samples.