Detecting N-RAS Q61R Mutated Thyroid Neoplasias by Immunohistochemistry

Recently, the immunohistochemistry (IHC) for N-RAS Q61R has been developed and commercialized for clinical practice. Here, we investigated the reliability of IHC to identify N-RAS Q61R mutated thyroid neoplasia. A series of 24 consecutive thyroid lesions undergone surgery following indeterminate cytology were enrolled. Paraffin sections were stained for IHC using the rabbit monoclonal anti-human N-RAS Q61R, clone SP174. N-RAS mutations in codon 61 were also investigated by automated sequencing. At histology, 12 cases of follicular carcinoma, cytologically defined as follicular lesions, 1 papillary cancer, 7 follicular adenomas, and 4 hyperplastic nodules were found. Of these, 4 showed a positive IHC for anti N-RAS antibody where N-RAS expression was detected mainly at cytoplasmic level with similar intensity of reaction. The remaining cases had negative IHC. A 100% concordance between IHC and molecular analysis for N-RAS Q61R was observed. In conclusion, this study shows high reliability of IHC to identify N-RAS Q61R mutated thyroid lesions with high cost-effectiveness. These data indicate the reliability of IHC to identify N-RAS Q61R mutated thyroid neoplasia and suggest to adopt this approach for a more accurate management of patients, when indicated.