Management of thyroid tumors diagnosed cytologically as follicular neoplasms in a high-volume center: utility of a scoring system using serum thyroglobulin level, tumor size, ultrasound testing, and cytological diagnosis

Managing thyroid nodules diagnosed cytologically as follicular neoplasms (FN) is challenging for patients and clinicians. Gene panel testing was recently introduced to determine the management strategy for FN; however, it is unavailable in Japan. In this study, we assessed FN management. This study included 2,144 FNs from 2,067 patients diagnosed between 2012 and 2018. Of these, 952 (44.5%) tumors underwent active surveillance, and 1,188 (55.6%) underwent immediate surgery (IS). Tumors of young patients (<55 years), male patients, and patients with serum thyroglobulin (Tg) ≥500 ng/mL, ultrasound diagnoses as FN or malignancy, large tumors (>4 cm), non-oxyphilic cytology, and cytological findings favoring malignancy and multiplicity underwent IS more frequently. Of the 1,412 tumors that underwent surgery, 279 (19.8%) and 1,133 (80.2%) were pathologically diagnosed as malignant and benign tumors or low-risk neoplasms, respectively. High Tg levels, non-benign ultrasound findings, cytological findings favoring malignancy, non-oncocytic cytology, and large tumor size were related to malignant pathology; however, tumor enlargement was not. The former three were independent predictors of malignancy in the multivariate logistic analysis. After assigning scores of 2 and 1 for cytological findings favoring malignancy and others, respectively, a receiver operating characteristic curve analysis indicated a score of 3 as the optimal cutoff for predicting malignant diagnosis; however, the area under the curve remained low, at 0.642. Accurately predicting the malignant pathology of FNs is challenging, and inducing gene panel testing will be helpful for managing FN tumors. Our scoring system would also be useful in estimating the risk of malignancy.