Endocrine Abstracts

Background: Thyroid nodules diagnosed as Bethesda category IV (follicular neoplasm/suspicious for follicular neoplasm (FN/SFN)) are recommended for surgery. However, only 25% of these nodules turn to be malignant on histopathology. Therefore, selection of nodules for surgery diagnosed as Bethesda category IV is important. We aimed at to define the predictive factors for malignancy and predictive risk indices for selection of surgery.

Method: The records of all patients with nodules that underwent fine needle aspiration biopsy (FNA) and classified by Bethesda reporting system as FN/SFN between 2011 and 2017 at our institution were reviewed. Univariate and multivariate analysis were performed to select independent factors associated with thyroid cancer. Using independent risk factors for malignancy predictive indices were created.

Results: Among 6,217 nodules which underwent FNA, 163 (2.6%) were diagnosed as FN/SFN. Of the 163 patients classified as FN/SFN, 126 underwent surgery with an associated malignancy rate of 36% (45/126). Age under 45, solid structure, microcalcification, hypoechogenicity and increased vascularization were found to be significant and independent risk factors associated for malignancy. The risk indices were created by classifying nodules with 0, 1, 2, 3, and ≥4 risk factors as risk indices 0, 1, 2, 3, and 4. There were 17 (14%), 41 (33%), 27 (21%), 22 (17%), and 19 (15%) patients in risk indices 0, 1, 2, 3, and 4, respectively. The estimated malignancy risk in patients with 0, 1, 2, 3, and 4 risk indices were 0% (0/17), 12% (5/41), 26% (7/27), 64% (14/22), and 100% (19/19), respectively.

Conclusions: Using predictive factors for malignancy in Bethesda IV category a small, but important proportion of patients 14% who had nodules without any risk factors could be spared unnecessary surgery. Predictive indices should be considered for informing the patients about the malignancy risk and for selection of surgery in Bethesda IV category.