Hyperfunctioning thyroid nodules are traditionally regarded as benign because hyperthyroidism rarely coexists with carcinoma, which unnecessary to do FNA. In clinical practice, however, many patients with suppressed thyroid-stimulating hormone (TSH) undergo FNA based on ultrasound risk stratification or discordant imaging findings. Surgical pathology occasionally reveals neoplasms arising within the hyperfunctioning focus. This study aimed to characterize the clinicopathologic features and frequency of such lesions in our cohort.

We retrospectively reviewed 82 patients with hyperthyroidism who exhibited a hot focus on thyroid scintigraphy at our institution between 2014 and 2024. Twenty-five patients (30.5%) subsequently underwent thyroid surgery for clinical or imaging indications. Cases were included for analysis when the hyperfunctioning nodule on scintigraphy corresponded anatomically to a surgically confirmed carcinoma or low-risk neoplasm. Coexisting non-functioning tumors and papillary microcarcinomas (≤1 cm) were excluded when functional correlation could not be determined.

Among all 82 hyperthyroid patients, 7 (8.5%; 95% CI 4.2–16.6%) had a neoplasm co-localized with a hyperfunctioning nodule. All seven patients presented with overt hyperthyroidism, comprising five females and two males with a median age of 48 years (range 24–68). Among the 25 surgical patients, 15 (60.0%; 95% CI 40.7–77.3%) were diagnosed with carcinoma or low-risk follicular-patterned neoplasms, while the remaining 10 had nodular goiter. Tumor size among the hot-nodule cases ranged from 1.3 cm to 8.6 cm (median 4.5 cm). Two patients underwent lobectomy and five patients received total thyroidectomy or completion thyroidectomy. No recurrence or metastasis was identified during follow-up.

In this 10-year single-center experience, approximately 8% of hyperthyroid patients had neoplasms arising within hyperfunctioning nodules, and 60% of surgical cases revealed neoplastic pathology overall. Functional autonomy does not exclude malignant or borderline potential. Careful multimodal evaluation remains warranted for hyperthyroid patients with nodules, particularly when ultrasound or cytologic findings appear incongruent with functional imaging.