Endocrine tumors occur more frequently during the feminine reproductive age, including pregnancy. Thyroid nodules are a common clinical disease; however, thyroid cancer is much less frequent and mixed carcinomas are rare. We report a case of mixed thyroid cancer with metastases to spine during pregnancy. Initially a mild peripheral neuropathy was confused with unspecific signs of pregnancy. Peripheral neuropathy became worse and after clinical and radiological investigation a tumor in thoracic column with compressive signals to the medulla was found. A decompressive surgery was performed and histological analysis revealed a malignant origin. Total thyroidectomy was performed and histological analysis evidenced three kinds of thyroid neoplasm (hyperplasic typical adenoma, papillary carcinoma and follicular medium differentiated carcinoma). Obstetric outcome was satisfactory evolution and a C-section was performed at 36 weeks. We report a rare case of thyroid malignant tumor occurring during pregnancy, in view of the few reports related in the literature. The present report may increase the knowledge about its clinical evolution, outcome and treatment.