Clinicopathologic characteristics of incidental thyroid carcinoma in euthyroid patients receiving total thyroidectomy for multinodular goiter: A retrospective cohort study.

[BACKGROUND] Total thyroidectomy is the treatment of choice for multinodular goiter (MNG). In some of these cases, incidental thyroid cancer (ITC) is detected postoperatively. Papillary thyroid microcarcinoma (PTMC), the most common type of ITC, has clinical factors and pathologic similarities with ITC that have not been well clarified previously. We investigated the incidence and characteristics of ITC and PTMC in euthyroid patients undergoing total thyroidectomy for MNG.

[METHODS] We retrospectively investigated the data of 151 euthyroid patients who underwent total thyroidectomy for MNG between January 2016 and December 2020. Patients with PTMC were then selected from among those with ITC for further data analysis.

[RESULTS] The incidence rates of ITC and PTMC were 31.1% (47/151) and 21.1% (32/151), respectively. The mean age of patients with ITC was 52.8 ± 11.7 years, which was younger than that of patients with benign MNG (57.2 ± 12.5 years, p < 0.05). Bilateral cancer was observed in 17 patients with ITC (17/47, 36.2%) and nine with PTMC (9/32, 28.1%). The numbers of patients in the ITC and PTMC groups whose cancer was not on the side comprising the dominant tumor were 15 (15/47, 31.9%) and 13 (13/32, 40.6%), respectively. The multivariate analysis demonstrated that younger age was a clinical factor associated with ITC and PTMC.

[CONCLUSION] Younger age is a clinical factor for ITC and PTMC. We recommend taking considering clinical factors and pathologic characteristics of ITC and PTC when considering total thyroidectomy in euthyroid patients with MNG.