A 32-year-old female is seen for a follow-up visit six months after undergoing total thyroidectomy and central neck dissection for medullary thyroid cancer. Pathology results revealed that the tumor was 3 cm in diameter, and 3 of 18 dissected nodes were positive for malignancy. The fasting serum calcitonin level before surgery was 250 ng/ml (normal

Question

A 32-year-old female is seen for a follow-up visit six months after undergoing total thyroidectomy and central neck dissection for medullary thyroid cancer.  Pathology results revealed that the tumor was 3 cm in diameter, and 3 of 18 dissected nodes were positive for malignancy.  The fasting serum calcitonin level before surgery was 250 ng/ml (normal < 4ng/ml).  The postoperative course was uncomplicated, and she was then started on levothyroxine 0.15 mg/d.  The repeat TSH level obtained after 8 weeks was normal.  The physical examination revealed no abnormal neck masses.  The rest of the examination is also unremarkable.  Her current calcitonin level is 120 ng/ml.  What is the next best step in the management of this patient?

Quizplus · Accepted Answer

Explanation: The patient has residual metastatic thyroid cancer, as suggested by the persistently elevated calcitonin levels. CT scan of the neck and chest with or without high-resolution ultrasound of the neck is recommended as the next step to look for metastatic disease. Surgical resection should be performed if a resectable lesion(s) is identified. If no lesion is identified, then an abdominal CT scan and bone scan may be required. I111 octreotide or PET scan may be helpful if CT scans are negative despite the presence of elevated calcitonin levels. (Choice C)Thallium scintiscan is nonspecific and has not been studied properly in patients with medullary thyroid cancer. (Choice B)Chest x-ray has a very low sensitivity for detecting metastatic lesions, and should not be used as a solitary investigative tool. (Choice E)Ultrasonography limited to the thyroid bed will not pick up lesion(s) in other parts of the neck. (Choice A)Medullary thyroid cancer is a malignancy of parafollicular C-cells that do not concentrate iodine; therefore, total body iodine scan is not useful in detection of metastasis of medullary thyroid cancer. Educational Objective: Elevated calcitonin levels in patients with medullary thyroid cancer following total thyroidectomy indicate metastatic disease. CT scan of the neck and chest is recommended as the next step to look for metastatic disease. Medullary thyroid cancer cells do not take-up iodine; therefore, total body iodine scan is not useful.

A 32-Year-Old Female Is Seen for a Follow-Up Visit Six