Fine-needle biopsy can accurately diagnose thyroid cancer in large nodules

09/21/2011
Having a large thyroid nodule does not necessarily indicate the presence of thyroid cancer, but physicians often recommend the use of an ultrasound-guided fine-needle aspiration biopsy (FNAB) in order to determine whether such a growth is benign or malignant.

Recently, a team of Korean endocrinologists from the Yonsei and CHA University Colleges of Medicine put the accuracy of these needle-based biopsies to the test.

Their results, which appeared in the journal Thyroid, may be encouraging for patients with undiagnosed thyroid growths. Researchers found that ultrasound-guided FNABs can determine whether a large thyroid nodule is malignant or benign with 98 percent accuracy.



Not all thyroid lumps are malignant. In fact, just 5 percent of nodules detected in the gland are found to be cancerous, according to the Columbia University Department of Surgery (CUDS).



It is precisely this low rate of cancer-to-nodules that makes precise cytopathological testing so important. Only with a needle-based biopsy can doctors know with any degree of certainty whether or not a patient has thyroid cancer.

To this end, physicians often order an ultrasound-guided FNAB. This simple test involves the insertion of a thin needle into a thyroid nodule. The needle itself is usually narrower than those used to draw blood, according to the CUDS. Patients usually do not even need local anesthetic.

After careful analysis of the removed tissue, researchers can usually determine if a patient has thyroid cancer.

The CUDS estimates that just 3 percent of all FNABs result in a false-negative, meaning a diagnosis of "benign" when in fact a nodule is cancerous. In the new study, researchers reduced that rate to 2 percent.

The team analyzed the use of FNABs in more than 660 cases of large thyroid nodules (meaning lumps at least 3 centimeters across). They compared the resulting diagnostic results to subsequent findings derived from thyroid surgeries or follow-up visits.

Researchers estimated that just one in 50 uses of FNAB results in a false-negative. The CUDS explains that failure to detect thyroid cancer in large nodules is often due to an inexperienced physician simply missing the nodule with the needle.

The National Institutes of Health emphasizes that this type of diagnostic test, along with coarse-needle biopsy, is still an indispensable part of thyroid cancer detection.