Clinicopathological features and prognostic factors analysis of multiple synchronous distinct subtypes of primary thyroid carcinoma

To investigate the clinicopathological features, diagnosis, treatment, and prognosis of multiple synchronous distinct subtypes of primary thyroid carcinomas.The clinical data of 68 cases of synchronous carcinomas of the thyroid (STC) admitted to the Department of Thyroid Surgery in our hospital from January 2013 to December 2021 were reviewed. According to the pathological type, they were divided into the Synchronous differentiated and differentiated thyroid Carcinoma (SDDTC) group (42 cases), the Synchronous medullary and differentiated thyroid Carcinoma (SMDTC) group (18 cases), and the Synchronous Anaplastic and differentiated thyroid Carcinoma (SADTC)group (8 cases). The diagnosis, treatment, and survival of patients in each group were analyzed.Women with coexisting thyroid cancer were predominant (59 cases). Most of the symptoms were found on physical examination (47.1%) and neck mass (45.6%). The median age of patients in the SDDTC group, SADTC group, and SMDTC group was 47.5 (28-74) years old, 68.5 (26-75) years old, and 56.5 (39-74) years old. The age of the SADTC group and SMDTC group was older than that of the SDDTC group (P = 0.04, P = 0.03), and the rate of lymph node metastasis in groups SADTC (62.5%) and SMDTC (55.6%) was higher than in group SDDTC (21.4%). The disease course time, tumor location, clinical stage, and mortality of the SADTC group were significantly different from those of the SDDTC group and SMDTC group (P < 0.05). The overall survival of patients with synchronous carcinomas of the thyroid was 6-105 months, and the median overall survival was 38.5 months. The tumor-free survival was 0-90 months, 19.1% of patients developed distant metastasis, 11.8% of patients had postoperative recurrence, as well as the survival rate was estimated 91.18%. Cox model multivariate analysis showed that cervical lateral lymph node metastasis and tumor stage III/IV were independent risk factors for progression-free survival(PFS). The comparison results of the survival curves showed that the overall survival (OS)of the patients in the SADTC group was significantly worse (P < 0.01), while there was no significant difference in the PFS of different pathological types (χ2 = 5.024, P = 0.081).The OS of different treatment methods was significantly different (P = 0.002), but there was no significant difference in OS between local recurrence and distant metastases with or without surgery (χ2 = 0.954, P = 0.329).The STC has relatively unique clinical characteristics, and most patients can get a better prognosis after radical surgery. Pathological type, lateral cervical lymph node metastasis, tumor stage, and treatment are important factors which affect the prognosis of the disease. Since there are two distinct tumors with different aggressiveness, treatment options, and prognosis, individualized management is required.