A single-institution study was done to investigate whether age of the patient affected the risk of developing malignancy in a large thyroid nodule (≥4 cm), which showed benign cytology on fine-needle aspiration biopsy (FNAB). Patients who underwent thyroidectomy for cytologically benign thyroid nodule from July 2008 to August 2019 were retrospectively reviewed. Patients who did not have cytology or final surgical histopathology reports or measurements of nodules were not included in the review.

The average nodule size for the entire cohort was 5.2 cm. Twenty-five of 474 nodules were found to be malignant on the final histopathology. Five (1.1%) nodules were found be highly suspicious with findings of microcalcifications, irregular margins, taller-than-wide shape, and/or peripheral rim calcifications on ultrasound reports. However, 98.9% nodules were either benign or had findings suggestive of very low, low, or intermediate suspicion. Therefore, ultrasound findings were not specific for the diagnosis of malignancy. 

About 41% patients had thyroid lobectomy and 59% had total thyroidectomy. Twenty-four patients (5.4%) were found to be malignant on final histopathology; 419 (94.6%) patients had benign nodules, of which 8 had non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). More patients below 55 years of age had malignant nodules versus those who were older than 55 years (7.7% vs 2%, respectively).

This study shows that in patients <55 years, the false-negative rate of a benign FNAB was 7.8%. Hence, thyroid lobectomy may be used as a diagnostic and therapeutic treatment strategy for this group of patients due to a higher risk of malignancy in large nodules. In patients >55 years, the rate of false-negative FNAB was 2.1%. In addition the size of nodules, indications of surgery in this age group also included compressive symptoms or substernal goiter. Patients who had ≥3 nodules that were ≥4 cm in size had a higher risk of malignancy.

The study concluded that patients <55 years with thyroid nodules ≥4 cm that were benign on cytopathology had a 3.7-fold higher risk of malignancy compared to their older counterparts indicating greater chances of false-negative results on cytopathology. Age therefore should be considered in treatment decisions for large nodules with benign cytology.

Sutton W, et al. Am J Surg. 2021 Jan;221(1):111-6