Nondiagnostic Fine Needle Aspiration of Thyroid Nodules: Review of Predisposing Factors

Fine needle aspiration (FNA) of thyroid nodules is the gold standard screening test for thyroid malignancy. Unfortunately, FNA may produce insufficient material for diagnosis. If nodules requiring FNA with a higher risk for nondiagnostic (ND) cytology could be identified pre-procedure, this might allow better patient guidance and potentially facilitate an altered approach to FNA.

The literature investigating risk factors for ND cytology was reviewed, including studies of patient factors, sonographic or nodule factors, and procedural factors. Twenty-five studies that included assessment of at least two potential factors in ND outcomes for initial FNA were identified. Individual factors were evaluated in terms of the general consensus of studies reporting either a positive significant association with ND cytology or no association.

Most patient and nodule factors lack consensus as far as their association with ND cytology across these studies. Factors where there are some consensuses include practitioner experience, depth of nodule, and cystic content; however, hypervascularity of the nodule does not appear to have a consensus.

A number of study design improvements suggested by this review could realistically be incorporated into higher powered future studies. Novel factors such as tissue composition anterior to the nodule or the age of the patient could also be investigated in future work. Operator experience is the most convincing procedural factor, and approaches to future studies of the FNA technique itself are proposed. That said, the factors with consensus among studies can be seen leading candidates for this future research, and the published studies illuminate a number of as yet unexplored factors that could in many cases be studied retrospectively.