According to the 2018 Recommendation of Polish Scientific Societies Diagnostics and treatment of thyroid cancer, which coincide with the 2009 ATA guidelines for adults, changes below 1 cm in diameter visible on ultrasound do not require referral for FNAB, unless clinical examination or ultrasound finds features of an increased risk of malignancy, RET mutation, high levels of calcitonin, or no thyroid cancer metastases in a location other than the thyroid gland. This evidence concerns the gene RET and thyroid cancer.