Abstract
In the WHO classification, 4th edition revised in 2017, regarding the pathological findings of conventional follicular variant of papillary thyroid carcinoma, non-invasive follicular thyroid neoplasm with papillary-like unclear features （NIFTP） and well-differentiated tumor of uncertain malignant potential （WDT-UMP） have been newly defined as tumors in the boundary region between benign and malignant tumors. We re-examined the pathological findings of thyroid cancer in 11 cases diagnosed as follicular variant of papillary thyroid carcinoma in our department. Of these, 4 cases were follicular variant of papillary thyroid carcinoma, 5 were NIFTP, and 2 were WDT-UMP according to the WHO classification, 4th edition. It was difficult to predict these pathological findings by preoperative ultrasonography, CT, and fine-needle aspiration cytology. In the future, genetic testing by fine-needle aspiration cytology may be used to predict pathological findings before surgery, and individualized treatment may be possible.
