Silent parathyroid adenoma mistakenly interpreted on FDG-PET as thyroid cancer metastasis in a patient with elevated thyroglobulin and negative I-131 whole body scan and removed by radioguided minimally invasive surgery.

Detection of recurrent and metastatic thyroid cancer remains a considerable challenge in patients presenting with rising thyroglobulin levels but with negative I-131 whole body scintigraphy. Such is the case in this patient with follicular thyroid cancer in whom subsequent FDG PET scanning showed a solitary hypermetabolic cervical lesion. With definitive management and multidisciplinary approach in mind, radioguided surgical excision came into play through the use of Tc-99m sestamibi, leading to successful removal of the lesion. Histopathology, however, revealed a parathyroid adenoma. This highlights the importance of considering differential diagnoses in apparent cases of recurrence to avoid potential pitfalls.