Most indeterminate thyroid nodules diagnosed with repeat fine-needle aspiration
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Repeat fine-needle aspiration can diagnose more than half of thyroid nodules initially classified as indeterminate, but diagnosis rates are less than 50% with nodules smaller than 0.5 cm or larger than 1 cm, according to study data.
“In this study, the definitive diagnosis rate of the second ultrasound-guided fine-needle aspiration of thyroid nodules was 51.8%,” Ming Yao, MMed, of the department of radiology at Hebei Province Hospital of Chinese Medicine in Shijiazhuang, China, and colleagues wrote in a study published in the Journal of Clinical Ultrasound. “In other words, half of the nodules that could not be given a definitive diagnosis by the first ultrasound-guided fine-needle aspiration were given one by the second ultrasound-guided fine-needle aspiration, thereby benefiting all these patients. However, the detection rate of different size nodules is not the same.”
Researchers conducted a second fine-needle aspiration (FNA) in 143 adults with 162 thyroid nodules at Hebei Province Hospital of Chinese Medicine from 2016 to 2017. The second FNA was conducted 3 months after an initial indeterminate FNA. Participants were included in the analysis if they had no tumor-related treatment between the two procedures and if they eventually underwent surgery producing pathology results. The nodules were divided by size into a small group with a diameter of less than 0.5 cm (n = 26), a medium group with a nodule diameter between 0.5 cm and 1 cm (n = 76) and a large group with a diameter larger than 1 cm (n = 60).
Of the 162 nodules in the study, 100 were confirmed to be malignant. In the small nodule group, 19 of 26 nodules were malignant, 42 of 76 nodules were malignant in the medium group, and 39 of 60 were malignant in the large group.
In the small group, eight of 26 nodules were diagnosed definitively after a second FNA, of which six were malignant. The other 18 nodules were not diagnosed definitively. Pathology results showed 13 of those 18 nodules were malignant.
In the medium group, 51 of 76 nodules were diagnosed definitively after repeat FNA, of which 34 were malignant. The other 25 modules were not diagnosed after the second FNA. Eight of those 25 nodules were malignant in pathology results.
In the large group, 25 of 60 nodules were diagnosed after a second FNA, with 19 diagnosed as malignant. The remaining 35 nodules were not diagnosed after repeat FNA, of which 20 were malignant in pathology results.
Overall, 51.8% of nodules were diagnosed after a second FNA. The diagnosis rate of nodules between 0.5 cm and 1 cm in diameter was 67.1%, significantly higher than the rate of 30.8% for nodules smaller than 0.5 cm and 41.7% for those larger than 1 cm (P < .05 for both).
Diagnosis accuracy after a second FNA was 95.2% overall. There was no significant difference in diagnosis accuracy between the three nodule size groups.
“A second ultrasound-guided FNA is recommended for thyroid nodules with diameter between 0.5 cm and 1 cm that cannot be definitively diagnosed by an initial ultrasound-guided FNA,” the researchers wrote. “However, the diagnostic efficacy of a second ultrasound-guided FNA appears to be low for nodules with a diameter less than 0.5 cm or greater than 1 cm, so it is recommended that further treatment of such nodules should be considered in line with clinical practice.”
Perspective
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Fine-needle aspiration biopsy of thyroid nodules is a quick and low-risk way to determine if thyroid nodules are benign or malignant. Unfortunately, about 15% of fine-needle aspiration results are cytologically indeterminate. Within the cytologically indeterminate group, 15% to 30% will ultimately prove to be malignant. Options for management of these lesions include ultrasound surveillance, re-biopsy, molecular testing to glean additional information regarding risk of malignancy, or surgery for definitive diagnosis. Molecular testing is not covered by all U.S. insurance carriers, and in that case out-of-pocket costs can be prohibitive. Surgery will prove unnecessary in the majority of cases since most will ultimately turn out to be benign.
The utility of repeat fine-needle aspiration biopsy on cytologically indeterminate thyroid nodules in an effort to make a definitive diagnosis was explored by Zhao and colleagues. Their study included nodules smaller than 1 cm, which is below the size typically recommended for biopsy by TIRADS and ATA criteria, but in their group of 60 nodules larger than 1 cm, a repeat fine-needle aspiration biopsy yielded a diagnosis in an additional 41.7%. Of the nodules larger than 1 cm diagnosed on repeat fine-needle aspiration biopsy, all nodules called malignant by repeat fine-needle aspiration biopsy were correctly diagnosed based on subsequent surgical pathology. However, 25% of those called benign by cytopathology, by repeat fine-needle aspiration biopsy were ultimately diagnosed malignant on surgical pathology.
This small series indicates that for nodules that are cytologically indeterminate on initial fine-needle aspiration biopsy, a repeat biopsy showing malignant findings is a reliable result, but a repeat result showing benign findings should not give a false sense of security. Nodules found to be indeterminate on a first fine-needle aspiration biopsy and then benign on repeat fine-needle aspiration biopsy should be considered for close ultrasound surveillance at minimum, but to be safer should undergo molecular testing or resection.
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