F-18 FDG PET detection of a medullary thyroid carcinoma in a patient with metastatic colonic cancer; literature review.

OBJECTIVE

We report a case of a medullary thyroid carcinoma discovered by F-18 fluorodeoxyglucose-positron emission tomography (F-18 FDG PET).

PATIENT AND

METHODS

A 73-year-old man with a history of surgical removal of sigmoid colon cancer underwent F-18 FDG PET to search for distant metastases and / or local recurrence because of elevated CEA level and new episode of occlusion. F-18 FDG PET images showed increased focal FDG uptake in the right lobe of the thyroid. Thyroid ultrasound showed one thyroid nodule in each lobe.

RESULTS

The fine needle aspiration result was suspicious and calcitonin level was elevated. The subject underwent thyroidectomy without lymph node dissection. The pathology showed a 14 mm medullary thyroid carcinoma. There was no germline mutation of RET.

CONCLUSIONS

F-18 FDG PET can detect primitive or secondary malignant thyroid tumors. Thus, thyroid incidentaloma revealed by 18 FDG PET uptake always necessitates careful evaluation.