[Skull base metastasis from differentiated thyroid carcinoma: 3 cases report and review of literature]

Skull base metastasis from differentiated thyroid carcinoma (DTC), including papillary and follicular thyroid carcinoma, is a rare manifestation and easily misdiagnosed. In this study, we reported three cases whose initial clinical presentation was skull base metastasis complaints with the presence of silent primary sites. Based on the thyroid ultrasound and histopathology (identifying skull base and primary thyroid tumor), the final diagnoses of DTC metastasis to skull base were confirmed. Two patients underwent removal of metastasizing tumors in the skull base and primary thyroid cancer, and have respectively survived 58 months and 4 months since then. Another patient underwent tumor removal of the metastasizing skull base carcinoma leaving the primary lesion intact. However, the patient died of recurrent carcinoma after 18 months. We compared the diagnosis and treatment processes of three patients with DTC metastasis to skull base, and referenced the reported cases in the literature. In conclusion, DTC metastasis to skull base is a rare occurrence and hence easy to be misdiagnosed as primary skull base carcinoma. Clinical records, imaging tests, histopathology and immunohistochemistry are mandatory for differential diagnosis and final diagnosis. Surgical resection of both the primary and metastatic lesions is the recommended treatment. In cases where tumors are removed completely via surgery, no further treatment is necessary postoperatively when meticulously following up is in place. However, in cases where tumors are postoperative residual, radiation therapy after surgery is a feasible option.