Follicular neoplasm Many patients will equate follicular neoplasm with follicular thyroid cancer, which is actually wrong. As mentioned before, FNA yields a cell smear, and follicular thyroid cancer has its own specific cytologic features compared to normal follicular epithelium, but this same cytomorphologic feature is present in adenoma cells. This means that FNA can detect abnormal follicular epithelial cells, but it does not distinguish whether such abnormal follicular epithelial cells originate from follicular adenocarcinoma or adenoma, so FNA cannot give a diagnosis of follicular adenocarcinoma as such (which is different from papillary, medullary, undifferentiated carcinoma, etc.). To arrive at a diagnosis of follicular thyroid carcinoma, one must rely on paraffin pathology to find evidence of invasion by membranes or blood vessels. Given the limitations of FNA in diagnosing follicular adenocarcinoma, the classification criteria for follicular neoplasms were proposed with the aim of prompting this group of patients to undergo surgical treatment. In terms of cases diagnosed as follicular neoplasm by FNA, approximately 35% are nodular goiter, so some hospitals also refer to this category as suspicious follicular neoplasm. In the WHO classification, Hürthle cell adenoma and Hürthle cell carcinoma are classified as subcategories of follicular adenoma and follicular adenocarcinoma, but in fact Hürthle cell tumor and follicular adenocarcinoma are genetically distinct. There is a genetic difference between Hürthle cell tumors and follicular tumors. Usually, surgery is recommended to remove the lobe of the lesion if it is diagnosed as a follicular tumor, but the treatment plan is individualized according to the patient’s condition, such as partial excision of the lobe if the preoperative thyroid ultrasound is highly suggestive of adenoma. Some patients may also opt for conservative treatment with regular review and repeat puncture. It is worth mentioning that molecular testing can provide some basis for differentiating benign from malignant.