Metastases to the thyroid gland: A retrospective analysis of 21 patients

Metastases to the thyroid gland are uncommon and often occur in patients with advanced metastatic diseases. The management and prognosis of secondary thyroid malignancies (STMs) are not well established. This retrospective study reported the incidence, clinical characteristics, treatment, and prognosis of STM in patients with metastatic tumors.

A total of 21 cases (1.2% incidence) diagnosed by fine-needle aspiration between January 2006 to December 2014 in a single center were reviewed. Survival analysis was made by Kaplan-Meier method.

The primary malignancies included esophagus cancer (7/21, 33.33%), breast cancer (6/21, 28.57%), head and neck cancer (3/21, 14.29%), unknown primary cancer (3/21, 14.29%), and lung cancer (2/21, 9.52%). The mean overall survival (OS) from diagnosis of primary malignancies was 57.26 months (95% confidence interval [CI]: 31.19-83.34) and the 2-year OS rate was 61.9%, and the mean OS from diagnosis of thyroid metastases was 31.20 months (95% CI: 12.23-50.18) and the 2-year OS rate was 34.3%. Patients with the head and neck cancer and breast cancer had better survival than other patients (from diagnosis of primary malignancies, P < 0.001; from diagnosis of thyroid metastases, P = 0.03). Histological types were also related to OS (from diagnosis of primary malignancies, P = 0.039; from diagnosis of thyroid metastases, P = 0.130). In addition, thyroidectomy may improve OS for patients with isolated metastases.

The prognosis of STMs basically depends on the anatomic sites and histological types of primary cancers, and thyroidectomy may be considered for patients with isolated metastases.