A Prospective Observational Study Assessing the Relationship Between Solitary Thyroid Nodule Size and Incidence of Malignancy

Background Solitary thyroid nodule (STN) is a well-documented entity. Autopsy data indicate a 50% prevalence of thyroid nodules >10 mm in patients without clinical evidence of thyroid disease. Prevalence of palpable nodules is 4-7%. Solitary thyroid nodules are often asymptomatic and found incidentally. Fine needle aspiration cytology is recommended to determine the nature of the thyroid nodule. 5-10% of the thyroid nodules are found to be malignant following thyroidectomy. Objective Our study aims to explore the relationship between solitary thyroid nodule size and malignancy. Methods A prospective, observational analysis looking at preoperative thyroid ultrasound scan findings and post-operative histology for a total of 100 female patients referred to our unit within a university hospital from November 2016 to April 2019. Statistical analysis including One-Way ANOVA was performed where appropriate. Results Total number of patients was 100 female patients divided according to the size of the nodule into three groups with the correlation between the size of the nodule and the incidence of malignancy. Group A: Patients with a STN <20 mm; eight patients; post-operative histology = all benign. Group B: Patients with a STN measuring 20-40 mm; 80 patients: 68 patients were benign, and 12 patients (12%) were malignant (incidence of malignancy in the group is 15%). Group C: Patients with a STN >40 mm; 12 patients: eight patients were benign, four patients were malignant, (incidence of malignancy = 33%). Correlation between the size of the nodule and the incidence of malignancy: Group A: 0/8 malignancy; Group B: 12/80 patients were malignant; Group C: 4/12 malignant. Conclusion Our results suggest that the size of a solitary thyroid nodule cannot be reliably used for at predicting malignancy and should not be influencing patient’s management.