A 61-year-old woman with newly diagnosed anaplastic thyroid cancer and known metastases to the brain, lungs, and adrenal glands complained of groin muscle pain. F-FDG PET/CT was performed to assess for extent of disease and showed extensive hypermetabolic lesions throughout the skeletal musculature concerning for metastatic disease. As this would be a very rare presentation for anaplastic thyroid carcinoma, a biopsy of the left gluteal muscle was conducted. Pathology demonstrated anaplastic thyroid carcinoma, metastatic to skeletal muscle.