The patient was a 40-year-old woman who was diagnosed with a malignant melanoma of the left posterior thigh. Follow-up positron emission tomography (PET)/computed tomography (CT) examination revealed an intensely FDG-avid lesion that predominantly contained fat in the right postero-lateral chest wall involving the latissimus dorsi. Ultrasound-guided fine needle aspirate and core biopsy confirmed the diagnosis of hibernoma rather than melanoma metastasis.