FNA showing follicular neoplasm (Bethesda IV) cannot tell adenoma from carcinoma, because the difference is capsular/vascular invasion, which cytology cannot show. The recommended step is surgery (lobectomy, i.e. diagnostic hemithyroidectomy) and histology, then completion total thyroidectomy if it is carcinoma. Core (Tru-Cut) biopsy is avoided in the thyroid, and an isotope scan or follow-up does not answer the question.