Analysis of the concurrent occurrence of medullary thyroid carcinoma and papillary thyroid carcinoma: A dual center, retrospective study in China.

This study examines the clinicopathological characteristics of patients with coexistent medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC). A retrospective analysis was conducted on 169 patients who underwent surgical treatment for MTC at 2 medical centers between 2010 and 2019. The clinicopathological characteristics were documented, and associations between MTC/PTC and MTC were evaluated. Among the 169 MTC patients, 16 (9.5%) exhibited concomitant histological characteristics of both MTC and PTC. Three patterns of carcinoma distribution were identified: mixed carcinoma, tumors confined to the ipsilateral glandular lobe, and MTC/PTC lesions dispersed across both glandular lobes. Of these 16 patients, 9 were female and 7 were male, with a mean age of 50.6 years. The PTC lesions had a maximum diameter of 0.40 ± 0.21 cm, whereas the MTC lesions measured 1.73 ± 1.86 cm in maximum diameter. Additionally, 9 cases exhibited lymph node metastases, but no distant metastases were observed. Univariate analysis indicated no significant associations between MTC/PTC and MTC (P > .05), with no differences in survival or prognosis between the groups.