Background: Fine-needle aspiration (FNA) is a useful method for evaluating a solitary thyroid nodule; however, this is not an agreed method for a multinodular goitre (MNG). The aim of this study was to assess the utility of preoperative FNA for detecting malignancy in MNG.
Patients and method: We analysed operated MNGs in which FNA had been performed. Puncture was carried out on the dominant nodule and any other nodules with features suggesting malignancy. The diagnosis was classed as colloid, follicular or Hurthle proliferation, suggestive of malignancy, haematic and inadequate. The thyroid FNA results, grouped into suggestive of malignancy (positive result) and other diagnoses (negative result), were compared to those of the final histological study in order to calculate the value of the test in diagnosing malignancy.
Results: FNA was performed in 432 MNGs, of which 42 (9.7%) were associated with carcinoma. Overall, the results of the test were poor, revealing a sensitivity of 17%, specificity of 96% and diagnostic accuracy of 88%, with a positive predictive value of 32% and negative predictive value of 88%. When the values were recalculated with the exclusion of microcarcinomas--considering their minor clinical importance--there was a slight improvement in the results: the sensitivity increased to 26%, diagnostic accuracy to 93% and negative predictive value to 96%. However, the specificity remained at 96%, and the positive predictive value fell from 32% to 25%. The results of the test improved in multifocal carcinomas.
Conclusions: Thyroid fine needle aspiration is not useful for differentiating MNG with malignant degeneration from benign MNG, as more than 80% of carcinomas go unnoticed; it provides a sensitivity of 17% for detecting carcinomas, rising to 26% if microcarcinomas are excluded. We therefore suggest that clinical criteria should prevail over FNA.