BRAFV600E and KRAS mutation in thyroid lesions: a study on Giemsa-stained fine needle aspiration archival smears

Introduction Molecular diagnosis is an important adjunct to FNAC in the evaluation of thyroid nodules, especially when cytology results are indeterminate. BRAFexon 15 p. V600E mutations in the thyroid have been shown to be almost exclusive to thyroid cancer. RAS protooncogene is also described in differentiated thyroid carcinomas and is used as tumor marker. However, their prevalence varies widely among studies, probably as a result of the detection methods used. In the present study, we evaluate the BRAFV600E and KRAS mutations in thyroid lesions on fine -needle aspiration archival smears and compare them with histological diagnosis Method This retrospective study was conducted in the department of Pathology for a period of five years: January 2020 to July 2024. All thyroid FNACs were reported and reclassified according tothe Bethesda system of reporting thyroid cytopathology system, 2023 and histological correlation wherever possible/available was included. Archival smears were used for DNA extraction for BRAF V600E and KRAS analysis by ddPCR. Results A total of 2300 thyroid FNAC were performed and categorised as TBSRTC 2023. Genomic extraction for BRAFV600E was done in 73 cases out of which 16 cases were positive. KRAS was done in all the BRAF positive cases and 6 cases showed both the mutations. BRAF expression and concomitant BRAF-KRAS expression was seen in 41.6% and 16.6% respectively of all the biopsy proven malignant cases. The risk of malignancy for BRAF+ FNAC smears was 90% and for BRAF-KRAS+smears, it was 100.