Impact of thyroid nodule location on the risk of papillary thyroid carcinoma.

Background: Thyroid nodules are a widespread disease in endocrine system. While ultrasound is the preferred non-invasive examination, it still has some limitations. The study aims to evaluate the correlation between the location of thyroid nodules and pathological diagnosis of thyroid cancer (TC).

Methods: We retrospectively reviewed data from medical records of patients with thyroid nodules who underwent thyroidectomy from 2018 to 2024. A total of 1307 patients with confirmed benign or malignant thyroid nodules were included.

Results: Nodules located in the lower part of left/right thyroid lobe had a higher frequency of malignancy (41.2%) compared to the isthmus (5.4%). A logistic regression model uncovered that the location of thyroid nodules was a significant risk factor for the diagnosis of TC (P = .044), both the upper [P = .040, odds ratio (OR) = 2.009] and the middle (P = .020, OR = 1.702) nodules in left/right lobe were distinctly malignant compared those in the lower. Adjusted by age, maximum nodule size, and aspect ratio, nodules in the middle part still had higher malignancy than the lower lobe (P = .046, OR = 1.630). We also evaluated the correlation between the location and capsular invasion. Compared with nodules in the lower part, non-lower nodules had a greater likelihood of invading the capsule, indicating a poorer prognosis for TC patients.

Conclusions: Our study showed that the location of thyroid nodules is an independent risk factor in determining TC. Nodules located in the lower part of the left/right lobe are considered as having the lower risk of malignancy and capsular invasion.