Abstract: Pediatric thyroid cancer is a malignant tumor of endocrine system. The early clinical symptoms are not typical, and parents are easy to ignore it. When the obvious symptoms or signs appear, the course of disease is often delayed for a long time, and lung shadow is found at this time, which is easy to be misdiagnosed as tuberculosis. Three cases of thyroid cancer reported in this study were misdiagnosed as hematogenous disseminated tuberculosis due to diffuse or multiple nodules in both lungs on chest imaging, and were recommended to be hospitalized in The Pediatrics Department of Guangzhou Chest Hospital. The disease course of the three cases all lasted more than half a year, and they had no history of tuberculosis (TB) exposure. After hospitalization, T-SPOT.TB for tuberculosis, and CT examination showed high possibility of pulmonary metastasis. The 3 cases were not diagnosed as disseminated pulmonary tuberculosis through comprehensive analysis. They were transferred to another hospital for diagnosis and treatment, we learned through telephone follow-up that they were both diagnosed with thyroid cancer and lung metastases.In recent years, the incidence of thyroid cancer in children in China has increased significantly. It is not easy to be detected in early stage and is prone to cervical lymph node metastasis and distant metastasis. Distant metastasis is one of the risk factors for poor prognosis. When pulmonary metastasis occurs, it is easy to misdiagnose as hematogenous disseminated pulmonary tuberculosis, thus delaying diagnosis and treatment, and losing the best treatment opportunity. Therefore, the differential diagnosis of pulmonary metastasis and hematogenous disseminated pulmonary tuberculosis should be emphasized in clinical work.

Key words: Children, Thyroid cancer, Hematogenous disseminated tuberculosis, Misdiagnosis