When an FNA biopsy is done and a nondiagnostic biopsy is returned, the FNA should usually be repeated. If it was a clear indication for a biopsy the first time, then a nondiagnostic result would mean that the patient is still in need of an accurate fine needle aspiration. The process of obtaining an FNA does generate inflammation within the gland of the thyroid and so repeat FNA should be delayed for a time which allows for a resolution of the inflammation. This helps to avoid conflicting biopsy results and increases the accuracy of the subsequent biopsy.
The other situation where a repeat FNA is often considered is in the face of an indeterminant result. While some people advocate for repeat FNA, this should be done with caution. Not all nodules contain uniform and homogeneous populations of cells. It is possible for a repeat FNA to pull out benign cells that are unlike the unusual cells that were seen on the first sampling. While this may appear reassuring for the patient that benign cells were seen, there is still a concern about the abnormal cells that were sampled during the first FNA. The better reason to consider a repeat FNA for indeterminant results is if molecular testing could be used to help further stratify the risk of cancer in a particular lesion. Molecular testing has added a significant degree of certainty to the indeterminant category and can be reassuring for increased probability of benign disease. Its use has obviated the need for surgical biopsy in many cases. Molecular testing is certainly an evolving area within the thyroid nodule evaluation, and it is critical that the performing surgeon understand the nuances of molecular testing and when it is appropriate to be used. Not all indeterminant lesions should undergo molecular testing and not all patients require this expensive testing. New advances in this area are coming at a rapid pace, so make sure your doctor has extensive knowledge and has kept up with the available molecular tests.