Unilateral Reduction of 18F-FDG Accumulation in Brown Adipose Tissue by Sympathectomy for Hyperhidrosis

A 30-year-old woman with left breast cancer underwent 18F-FDG PET/CT for staging. Intense FDG uptake was observed in the primary lesion, as well as on the left side of the neck to the supraclavicular fossa and left paravertebral region. History taking revealed that she had undergone a right thoracic sympathectomy for hyperhidrosis, which resulted in attenuated FDG uptake in the right-sided brown adipose tissue (BAT). With another examination keeping adequate warming, the accumulation of BAT was reduced and a diagnosis of cT1N1M0 was made. Unilateral sympathetic blockade can cause asymmetric FDG accumulation in BAT, which interferes with interpretation in tumors.