Are solitary thyroid nodules more likely to be malignant?

Traditional teaching demonstrated that solitary thyroid nodules were more likely to be malignant. Newer studies show that there is no clear answer regarding the influence of the number or the distribution of nodules on the risk of malignancy.

The purpose of this study was to establish whether patients undergoing thyroid surgery and presenting with a solitary thyroid nodule show a greater rate of malignancy when compared to those presenting with multiple nodules. The secondary goal was to evaluate the impact of the distribution of the nodules (multiple unilateral nodules versus bilateral nodules) on the rate of malignancy in this population.

Retrospective review of the medical records of the 656 patients who underwent thyroidectomy at one of the hospitals of the McGill University Thyroid Cancer Centre between July 2006 and April 2011 was conducted.

There was no significant difference in the malignancy rate between patients with a solitary nodule and patients with two to six thyroid nodules at ultrasonography, between patients with unilateral nodule(s) and patients with bilateral nodules, or between patients with at least one nodule > 1.0 cm and patients without any nodules > 1.0 cm (p  =  .870, .578, and .361, respectively).

This study demonstrates that the likelihood of thyroid cancer is independent of the number of thyroid nodules. Moreover, our data show that the malignancy rate is not influenced by the distribution of the nodules or their size.