Large, Slowly Growing, Benign Thyroid Nodules Frequently Coexist With Synchronous Thyroid Cancers.

[CONTEXT] Thyroid nodules' size should not be the sole criterion for thyroidectomy; however, many patients undergo surgery for large or slowly growing nodules.

[OBJECTIVE] We evaluated risk for clinically significant thyroid cancer in patients with large or slowly growing nodules.

[METHODS] We reviewed data from 2 prospectively collected databases of patients undergoing thyroidectomies in tertiary referral centers in the USA and Greece over 14 consecutive years. We collected data on the preoperative surgical indication, FNA cytology, and surgical pathology. We included subjects operated solely for large or growing thyroid nodules, without any known or presumed thyroid cancer or high risk for malignancy, family history of thyroid cancer, or prior radiation exposure.

[RESULTS] We reviewed 5523 consecutive cases (USA: 2711; Greece: 2812). After excluding 3059 subjects, we included 2464 subjects in the present analysis. Overall, 533 thyroid cancers were identified (21.3%): 372 (69.8%) microcarcinomas (<1 cm) and 161 (30.2%) macrocarcinomas (≥1 cm). The histology was consistent with papillary cancer (n = 503), follicular cancer (n = 12), Hürthle cell cancer (n = 9), medullary cancer (n = 5), and mixed histology cancers n = 4. Only 47 (1.9%) of our subjects had any form of thyroid cancer in the nodule that originally led to surgery. The cancers were multifocal in 165 subjects; had extrathyroidal extension in 61, capsular invasion in 80, lymph node involvement in 35, and bone metastasis in 2 subjects.

[CONCLUSION] The risk of synchronous, clinically important thyroid cancers is small, but not null in patients with large or slow growing thyroid nodules. Therefore, more precise preoperative evaluation is needed to separate the patients who would clearly benefit from thyroid surgery from the vast majority of those who do not need to be operated.