Physiologically Variant FDG Uptake in Scalene Muscle Mimicking Neck Lymph Node Metastasis in a Patient with Lung Cancer

Physiologic variant FDG uptake in scalene muscle has be recognized as a potential pitfall in head and neck PET or PET/CT. The patterns of uptake are usually bilateral, symmetrical and linear; and the intensity is low. We herein presented a lung cancer patient with painful chest wall invasion undergoing FDG-PET/CT for follow-up. There was unilateral, focal and unusually high FDG uptake (SUVmax = 8.39) in left lower neck on PET/CT images, which was initially considered as lymph node metastasis. No palpable nodular lesion was found in neck on physical examination. Re-inspection of the co-registered CT and fused PET/CT images localized the uptake in scalene muscles. Further MRI studies revealed no any abnormal signal of suggesting malignancy or inflammation in neck. Physiological variant scalene muscle uptake secondary to pain-related muscular strain was finally concluded.