For indeterminate thyroid nodules following fine needle aspiration, evidence of thick post-microcystic reflection on ultrasound was found to be associated with malignant nodules, according to study results presented at the American Association of Clinical Endocrinologists 28th Annual Scientific & Clinical Congress, held April 24 to 28, 2019, in Los Angeles, California.

Molecular mutation may assist in risk assessment of thyroid nodules that are indeterminate on fine needle aspiration, but the costs of this test is high. The study researchers aimed to analyze the association between ultrasound characteristics and malignancy of indeterminate thyroid nodules.

Experienced ultrasonographers reviewed the imaging of thyroid nodules >1 cm from 204 patients who had biopsies performed between January 2015 and December 2016. All thyroid nodules were found to be indeterminate (Bethesda III, IV, or V) or Bethesda VI.

Of 153 indeterminate thyroid nodules with available pathologic results, 91 (59.5%) were benign and 62 (40.5%) were found to be malignant. All 51 Bethesda VI nodules were malignant. Classic papillary thyroid carcinoma was the most common type of malignancy (35.3%), followed by follicular-variant papillary thyroid carcinoma (9.8%), noninvasive follicular thyroid neoplasm with papillary-like nuclear features (4.9%), follicular thyroid carcinoma or Hurthle cell carcinoma (2.5%), and other types (3%).

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In most cases of indeterminate nodules (65.1%), ThyroSeq® V.2 molecular testing was positive for mutations. In the group of indeterminate nodules that were found to be malignant, high-risk mutations were significantly more common compared with indeterminate nodules that were benign (81.4% vs 36.8%; P <.01).

Other than the known radiologic features that have been associated with malignant thyroid nodules, the researchers reported that intranodular thick post-microcystic linear reflection without reverberation was significantly associated with malignant nodules with a high specificity. This feature was evident in 64.7% (33/51) of Bethesda VI nodules and 36.3% (41/113) of indeterminate nodules that were found to be malignant. However, thick post-microcystic reflection was not seen in any of the 91 benign indeterminate nodules.

Statistical analysis revealed that regardless of mutation status, thick post-microcystic reflection was significantly associated with malignancy (P <.01).

In contrast, thin post-microcystic reflection was more common in benign indeterminate nodules (44/91 nodules; 48.4%; P <.01) but was also found in the malignant nodules (26/113 nodules; 23%).

“After future validation, thick [post-microcystic reflection] may be a significant [ultrasound] feature similar to microcalcification, solid composition, hypoechogenicity, and infiltrative margins useful in risk classification of [thyroid nodules] for malignancy,” concluded the investigators.

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Reference

Waisayanand N, Goundan P, Guan H, Toraldo G, Lee S. New ultrasound characteristic to predict malignancy in indeterminate thyroid nodules. Presented at: American Association of Clinical Endocrinologists 28th Annual Scientific & Clinical Congress; April 24-28, 2019; Los Angeles, CA.