Tumor Size Predictive for Malignancy in Indeterminate Follicular Thyroid Lesions

Fine needle aspiration biopsy is of little value in distinguishing benign and malignant thyroid follicular neoplasms. In this study, we investigated clinical and histopathologic characteristics of cytologically indeterminate thyroid follicular lesions (ITFL) in attempt to predict malignancy as determined by histopathologic examination. Fifty-seven patients diagnosed with ITFL underwent thyroidectomy. The mean patient age was 50.4 +/- 13.4 years. Based on the histopathologic findings, cases were classified into 3 categories: nonfollicular lesion (NF), follicular adenoma (FA), and follicular carcinoma (FC). The NF group contained 19 subjects with nodular colloidal goiter (NCG), 3 with Hashimoto thyroiditis. and one with granulomatous thyroiditis. The FA group contained 7 classic follicular and 8 Hurtle cell adenomas. The FC group contained 6 classic follicular, 8 Hurtle cell, and one insular carcinoma. The mean nodule size was significantly larger in the FC group than in the FA and NF groups (4.2 +/- 2.4 cm vs 2.2 +/- 0.9 cm and 2.5 +/- 1.3 cm, respectively, P < 0.05). Using a value of nodule size of 3 cm, the sensitivity and specificity for solvent malignant histology are 66.7% and 83.3%, respectively. These data show that nodule size of ITFL is predictive of malignancy. A nodule size greater than 3 cm is associated with a higher probability of malignancy and suggests total thyroidectomy as an initial therapeutic intervention.