The indeterminate thyroid fine‐needle aspiration

Abstract

BACKGROUND: To date, thyroid fine‐needle aspiration (FNA) has been used by clinicians as the screening test of choice to determine whether surgery is required and this is what the pathology report should communicate. Standard terminology for reporting thyroid FNA has not been implemented yet, and pathologists have used various reporting systems to communicate results. A significant source of confusion among both pathologists and clinicians has been the use of the indeterminate category. On the basis of an analysis of 1150 thyroid FNAs in 2000, this institution modified the reporting of thyroid biopsy results into 6 categories, including unsatisfactory. The indeterminate category was separated into 3 subroups: 1) indeterminate for neoplasia (IND), 2) follicular neoplasm (FN), and 3) suspicious for malignancy (SUSP). Repeat FNA in 6 months to 12 months was recommended for IND and surgery for FN and SUSP categories. METHODS: To determine the validity of this approach, the outcomes of this reporting system from July of 2000 to December of 2006 were analyzed. The IND category was used for 2 subsets of cases: (a) those that morphologically fall into the gray zone between adenomatoid nodule (AN) and FN, for Hurthle cell nodule (hyperplasia vs neoplasm), and chronic lymphocytic thyroiditis with concern for neoplasia; and (b) for suboptimal specimens due to low epithelial cellularity or collection artifacts. RESULTS: Among 5194 thyroid nodules, the IND category comprised 18%. FNA follow‐up was done in 21% of IND cases: 58% were benign/negative and did not require surgery based on cytology alone. Surgical follow‐up in 46% of IND showed 52% were benign/negative, and 42% were follicular/Hurthle cell adenomas. The surgical yield of malignancy in IND was low (6%) when compared with the FN category, which was 14% (more than 2× that of the IND category), and the SUSP category, which was 53% (almost 9× that of the IND category). CONCLUSIONS: A 6‐tier reporting system for thyroid FNA was effective for determining which patients needed surgery versus follow‐up FNA and also guided the clinician on the extent of surgery. Cancer (Cancer Cytopathol) 2009. © 2009 American Cancer Society.