Molecular Alterations in Suspicious for Follicular Neoplasm (Oncocytic Type) Category of The Bethesda System for Reporting Thyroid Cytopathology

Summary: Introduction: The suspicious for follicular neoplasm (oncocytic type) category of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has molecular testing to help guide management. Currently available testing panels are Thyroseq version 3, Afirma and Quest. We aim to determine the molecular alterations in suspicious for follicular neoplasm (oncocytic type) category. Materials and Methods: This is a retrospective study of reports of suspicious for follicular neoplasm (oncocytic type) category for last 5 years. The resection of these lesions categorized as benign, NIFTP and malignant. The risk of malignancy (ROM) calculated both from the surgical resection and the Thyroseq reports (MDROM). The molecular alterations are noted in the benign and malignant resections. Results: Total of 212 cases have been included in the study. M:F ratio was 1:2.93 with median age 61 years. The nodules were in left lobe (104), right lobe (99) and isthmus (9). Molecular work-up was performed in 192 cases which included Thyroseq (88), Afirma (15), Quest (89). A total of 76 cases underwent surgical resection of which benign were 39, malignant were 36 and 1 was Non-invasive follicular thyroid neoplasm (NIFTP). Out of 36 malignant cases, 30 cases had molecular work-up performed. ROM for cases with surgical resection was 47.36% (36/76), ROM for cases with molecular work-up were 39.47% (30/76), ROM for the total cohort was 16.98% (36/212), MDROM (Thyroseq) for surgical resections was 74.69% The molecular alterations in benign and malignant resections are summarized in table 1 and 2. NIFTP case showed NRAS mutation by Thyroseq testing. Conclusions: MDROM (Thyroseq) was higher compared to ROM by surgical resections. Thyroseq version3 testing was the most frequently used modality of testing in the surgically resected cases. The majority of molecular alterations of our study were in conjunction with the current literature for oncocytic neoplasms.