Should all thyroid nodules that are larger than 4cm be removed based solely on their size?
Thyroid nodules are very common, up to 67% of people have them. We assess them with the use of thyroid ultrasound. There are ultrasound criteria called TI-RADS that guide us thyroid surgeons and physicians which nodules should or should not be biopsied. And we act based on the results of the biopsy.
If the biopsy shows cancer or suspicion of cancer, then this leads to thyroid surgery. If thyroid biopsy has shown the benign result, but the patient had large nodule>4cm, then we have still recommended thyroid surgery as prior studies have shown that these nodules are associated with a higher rate of cancer.
But should we do this?
To investigate the latest large study from Chicago has helped us answer this question. This was based on looking at 2 important things:
Is the size of a nodule on its own associated with increased risk of cancer?
Is there a higher likelihood of falsely negative biopsy result in larger nodules? Meaning we have a sampling error due to the size of the nodule (by chance we have sampled part of the nodule that does not have cancer cells in it)
So what has this study show us?
The study has shown that the rate of malignancy in thyroid nodules that are over 4cm is around 20.9% which is the same or just slightly higher than the rate of cancer in nodules that are less than 4cm (19.9%). So size alone cannot be used to tell us which nodules are cancerous or not. We have known this for a long time, but it was nice to confirm this.
The more important question is whether there is a higher likelihood of a false negative biopsy result.
The rate of a false negative result is slightly higher in those nodules that are 4cm or larger (6.7%) vs those with nodules smaller than 4cm (4.5%). This difference was not statistically significant.
I am so grateful to these researchers as this helps me advise my patients who have large nodules with benign biopsy result. Now I can let my patients know that if they have large benign thyroid nodule which is not causing him or her any problems, that it is safe to observe them and that the surgery is not necessary.
If these large thyroid nodules are growing or causing problems with breathing, pressure, voice, swallowing etc., then these nodules should be removed.