Gluteal Muscle Metastasis of Papillary Thyroid Cancer with Increased Somatostatin Receptor Expression in Ga-DOTATATE PET/MRI.

A 56-year-old male patient underwent total thyroidectomy, and pathology revealed multicentric papillary thyroid cancer. His post-operative stimulated thyroglobulin value was >500 ng/mL. F-fluorodeoxyglucose positron emission tomography (PET) computed tomography revealed hypermetabolic metastatic pulmonary nodules, cervical, and mediastinal lymph nodes. There was also a hypermetabolic lesion in the left gluteal muscle. Due to the patient's history of a pilonidal cyst in the same region, the possibility of an abscess was also considered, and due to the absence of radioactive iodine (RAI) uptake in the lesion, follow-up was deemed appropriate. During follow-up, as the patient progressed to RAI-refractory state, Ga-DOTATATE PET/magnetic resonance imaging, which was done for radionuclide therapy planning, revealed heterogeneously increased uptake in the gluteal lesion. A subsequent biopsy confirmed the diagnosis of PTC metastasis.