Sonographic and pathologic features of malignant hot thyroid nodules: A multi-institutional study.

Background: Prior studies indicate that approximately 5% of hot thyroid nodules harbor malignancy. Hot nodules often exhibit suspicious sonographic features despite their typical benign pathology. This study examines the incidence, sonographic characteristics, and surgical pathology of malignancy within hot nodules to guide workup of these nodules, including preprocedure workup for thermal ablation.

Methods: Patients at 5 tertiary care centers with solitary toxic nodules or toxic multinodular goiters undergoing thyroidectomy (2017-2024) were included. Using thyroid uptake scan and ultrasonography, hot nodules were matched with sonographic characteristics. Nodules <1 cm and patients without either imaging were excluded. Sonographic features and indications for biopsy were assessed using the Thyroid Imaging Reporting and Data System classification. Kruskal Wallis and tests of proportions were used for analysis.

Results: Among 257 patients with 323 hot nodules, 11 (3.4%) nodules were malignant: 9 of 124 (7.3%) solitary toxic nodules and 2 of 199 (1.0%) in multinodular goiters (P = .003). Compared with benign hot nodules, malignant hot nodules were more often solid (90.9% vs 51.6%, P = .01), isoechoic/hyperechoic (81.8% vs 48.4%, P = .04), and biopsied (81.8% vs 41.7%, P = .008). Pathology of malignant hot nodules revealed papillary and follicular cancers with BRAF positivity (36.4%), lymphovascular invasion (45.5%), multifocality (36.4%), and tall cell features (33.3%). Providers recommended completion thyroidectomy for 2 patients and postoperative radioactive iodine for 3.

Conclusions: Solitary toxic nodules harbor a higher risk of malignancy than toxic multinodular goiters, and these malignancies can exhibit poor prognostic pathologic features. The 7.3% malignancy rate in resected solitary toxic nodules may support existing recommendations for biopsy prior to thermal ablation of these nodules.