Malignancy risk assessment in adenomatoid nodules and suspicious follicular lesions of the thyroid obtained by fine needle aspiration cytology.

Our aim was to assess malignancy risk in adenomatoid nodules and suspicious follicular lesions of the thyroid obtained by fine needle aspiration (FNA) cytology. Retrospective research was performed of 276 patients who underwent thyroid surgery after preoperative ultrasound-guided FNA diagnosis of either adenomatoid nodule, cellular follicular lesion, "suspicious for follicular neoplasm" or follicular neoplasm. Out of 276 patients, FNA reports showed 15 diagnoses (5%) of adenomatoid nodules, 73 (26%) cellular follicular lesions, 76 (28%) "suspicious for follicular neoplasm", and 112 diagnoses (41%) of follicular neoplasm. FNA reports were compared with pathohistological findings. In FNA reports of adenomatoid nodule (N = 15), there were seven (47%) pathohistological diagnoses (PHDs) of nodular goiter, and eight (53%) PHDs of follicular adenoma. In FNA reports of cellular follicular lesion (N = 73), there were 2 (3%) PHDs of thyroiditis, 32 (44%) PHDs of nodular goiter, 38 (52%) PHDs of follicular adenoma, and one (1%) PHD of papillary carcinoma. In FNA reports of "suspicious for follicular neoplasm" (N = 76), there was one (1%) PHD of thyroiditis, 24 (32%) PHDs of nodular goiter, 47 (62%) PHDs of follicular adenoma and four (5%) diagnoses of papillary carcinoma. In FNA reports of follicular neoplasm (N = 112), there were 25 (22%) PHDs of nodular goiter, 72 (64%) PHDs of follicular adenoma, and 15 (14%) PHDs of thyroid carcinoma. We found significant difference (p < 0.01) between investigated FNA report groups according to malignancy risk. Stratification of cytologic diagnoses of follicular thyroid lesions into different subcategories with various probabilities of malignancy allows more accurate estimation of malignancy risk and individualized patient treatment, when deciding between immediate operation and close follow-ups with repeat FNA.