Spherical thyroid nodule tied to greater risk of malignancy

A spherically shaped thyroid nodule, as indicated by a long-to-short ratio approaching 1.0, is associated with a higher risk of malignancy, irrespective of age, sex, and nodule size, suggests a study.

“Incorporating a nodule’s sphericity in the risk stratification systems may improve individualized clinical decision making,” the authors said.

This prospective cohort study was conducted at a single large academic healthcare system in the US and included patients with one or two clinically relevant thyroid nodules (predominantly solid and over 1 cm) presenting for diagnostic evaluation. The following procedures were performed: thyroid ultrasound, cytological evaluation with fine-needle biopsy, and/or histopathological examination on occasion of thyroid surgery.

The authors calculated the nodule’s long-to-short ratio (spherical shape) and examined its association with tissue proven benign or malignant endpoints.

Malignant nodules had significantly lower long-to-short nodule ratio than benign ones, indicating greater risk of malignancy in more spherical nodules (1.63 vs 1.74 cm; p<0.0001). The malignancy risk continued to increase as the long-to-short ratio approached a purely spherical ratio of 1.0 (ratio >2.00, 14.6 percent cancer; ratio 1.51‒2.00, 19.7 percent; ratio 1.00‒1.50, 25.5 percent; p<0.0001).

Younger age, male sex, and nodule’s spherical shape independently correlated with the risk of cancer in multiple regression analysis.

“Predictive models of thyroid nodule cancer risk are presently based upon nodule composition, echogenicity, margins, and the presence of microcalcifications,” the authors said. “Nodule shape has shown promise to be an additive factor helping determine the need for nodule biopsy.”