Thyroid bed fine needle aspiration in patients after thyroidectomy--a useful follow-up tool with proposed diagnostic categories.

After thyroidectomy for primary thyroid malignancies, patients are closely monitored for recurrence or metastasis. Fine needle aspiration (FNA) has been used as the appropriate diagnostic modality for occult masses identified radiographically in the thyroid bed. In this study, we report our institutional experience with FNA of the thyroid bed and propose practical diagnostic categories. A retrospective chart review of all thyroid bed FNAs between April 2008 and January 2013 was performed, and a cohort of 39 patients was retrieved. The cytology diagnoses were divided into 5 categories including nondiagnostic, inflammatory/reactive, bland follicular cells, suspicious for neoplasm/malignancy, and malignant. The follow-up histologic and/or clinical findings were collected for each category. The 39 patients included 9 males and 30 females (ages 15-79 years). Prior thyroidectomies were due to papillary thyroid carcinoma (31 cases), follicular carcinoma (3 cases), medullary carcinoma (1 case), Hürthle cell carcinoma (1 case), malignancy unspecified (1 case), follicular adenoma (1 case), and multinodular goiter (1 case). Overall, 33% (13 cases) of thyroid bed FNAs were nondiagnostic, and 10% (4 cases) were categorized as "inflammatory/reactive." None of the patients in these 2 categories demonstrated evidence of clinical recurrence. One patient with a "bland follicular cells" thyroid bed FNA diagnosis had metastatic papillary thyroid carcinoma on follow-up histology. Of 14 patients in the "suspicious" and "malignant" categories, 10 had malignant follow-up diagnosis on histology. In conclusion, thyroid bed FNA with standardized diagnostic categories is a useful modality for follow-up in patients who have undergone thyroidectomy.