The spherical shape of a solid thyroid nodule suggests an increased risk for thyroid cancer, according to a study from the United States published in the July 2022 issue of the Journal of Clinical Endocrinology & Metabolism.¹

Patients with thyroid nodules more than 1 cm in size and mainly solid in consistency were included in this single-center prospective cohort study. They underwent thyroid ultrasound, FNAC and/or histopathological examination at the time of resection. The long to short ratios of the nodules were also measured. With this information, the researchers set out to discover if the shape of the nodule and the risk of cancer were linked.

Results showed that the long to short nodule ratio was much lower in malignant nodules (1.63) compared to benign nodules (1.74) indicating that nodules that were more spherical in shape had greater chances of being malignant. The risk for cancer was 14.6% if the ratio was > 2.00, for ratio ranging between  1.51 and 2.00, the risk of malignancy was 19.7%. As the ratio reached 1.00 (1.00-1.50), the risk increased to 25.5%. On multiple regression analysis, the researchers noted, “younger age, male sex, and nodules spherical shape were each independently associated with cancer risk”.

The correlation of thyroid nodule size with the risk of cancer is well established. This study has shown that the shape of the solid thyroid nodule is also associated with an increased risk of malignancy. The closer the shape of the nodule reached a sphere, as evident by the long to short ratio of 1.0, greater were the odds of the nodule being malignant. Hence, the shape of the nodule may help in the clinical risk assessment of thyroid malignancy preoperatively and “improve individualized clinical decision making”. The final diagnosis though is by way of FNAC and histopathology.

Reference

1. Pappa T, et al. Thyroid nodule shape independently predicts risk of malignancy. J Clin Endocrinol Metab. 2022 Jun 16;107(7):1865-1870. doi: 10.1210/clinem/dgac246.