麻豆传媒

BOSTON -- Location of a thyroid nodule may help predict whether or not it's malignant, researchers reported here.

In a late-breaking abstract presented at the annual meeting of the , nodules located in the upper pole on ultrasonography had a higher frequency of malignancy compared to other locations (OR 5.8, P=0.01):

• Upper pole: 28.6% malignant (4 out of 14)
• Lower pole: 4.9% (7 out of 142)
• Middle pole: 18.2% (2 out of 11)
• Isthmus: 14.3% (1 out of 7)

The study, conducted by Fan Zhang, MD, PhD, of Brookdale University Hospital Medical Center in Brooklyn, New York, and colleagues, also found upper pole nodules had a significantly higher odds of being malignant even after adjustment for size, laterality, and number of thyroid nodules, as well as age, gender, and BMI (OR 4.6, P=0.03).

"Our study is the first report showing that thyroid nodules located in upper pole can be considered as a higher-risk factor of malignancy," Zhang explained to 麻豆传媒. "It surprised me initially since nobody has studied or reported before."

However, Zhang noted her group postulated that one of the likely mechanisms behind these findings may be explained by "the slow venous drainage of the upper lobes due to the tortuous route of the superior and middle thyroid veins [that] may be a possible reason for the increased incidence of malignant nodules in the upper poles compared to the lower lobes, which are drained by the inferior thyroid veins directly into the subclavian or brachiocephalic veins. Reactive oxygen species may be accumulated and induce malignant tumor through various cell signaling pathways."

The retrospective analysis included data on 219 individuals who had undergone fine-needle aspiration biopsy on a thyroid nodule, 86.2% of whom were female. A total of 31 patients were classified as Bethesda I and were therefore excluded from the analysis.

In general, thyroid nodules were equally split between the right and left lobes, while only around 2% were located in the isthmus. Some 40% of patients had multiple thyroid nodules. The majority (79%) were located in the lower pole, while less than 10% were located in the upper pole, and only 7% were in the middle pole. In total, 7.4% of all thyroid nodules were found to be malignant.

Because of the high prevalence of thyroid nodules, Zhang explained her group wished to conduct this study in order to develop a more accurate assessment of nodules in order to help avoid unnecessary biopsies and overtreatment. "Some sonographic characteristics of nodules are well known to be associated with malignancy, such as microcalcifications, hypoechoic, infiltrative margins, increased vascularity, and taller than wide," she noted, but added that no previous studies have identified the link between location of nodules in the upper pole with a higher likelihood of malignancy.

Based on these findings, Zhang recommended that the location of thyroid nodules should be considered as inclusion criteria within the "to enhance the predictive value of malignancy, diagnostic accuracy and reliability as indication to perform fine-needle aspiration."

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