Medullary thyroid carcinoma (MTC), a relatively rare neuroendocrine tumor originating in parafollicular C cells, releases calcitonin and carcinoembryonic antigen (CEA). A 52-year-old female woman with MTC had idiopathic abnormally elevated serum CEA for 2 years. Fluoro-deoxy-glucose positron emission tomography (FDG-PET) identified an intensive signal mass in the right thyroid lobe. Sporadic MTC was clinically diagnosed from typically high serum CEA and calcitonin. Following total thyroidectomy and D1 and deep cervical lymph node dissection, the woman remains free of distant metastasis and recurrence in the three years since surgery.
MTC in our case grew very slowly. The ratio of calcitonin to CEA was 14.7. FDG-PET is useful for detecting thyroid tumors and for follow-up if recurrence is suspected. The calcitonin- to -CEA ratio is a valuable parameter in clinical prognosis of this malignant tumor as reported in previous studies.
