Symmetric Supraclavicular and Paravertebral Uptake in a Young Patient With Lymphoma
A 23-year-old woman with Hodgkin lymphoma undergoes interim FDG PET/CT in January. She fasted for 6 hours and rested in a cool waiting room for 50 minutes before injection. Her blood glucose is 88 mg/dL. The PET/CT shows symmetric, intense FDG uptake in the supraclavicular, paravertebral, and axillary regions, with SUVmax 5.2. There is also a 1.8-cm left cervical lymph node with SUVmax 3.1. The patient is asymptomatic. The referring hematologist asks whether the symmetric uptake represents progressive lymphoma and whether a repeat scan should be done. The scan was performed 60 minutes after injection of 370 MBq FDG on a time-of-flight scanner. She denies shivering but says the room was cold.
1. What is the likely cause of the symmetric uptake, and how does it affect interpretation?
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The symmetric distribution in the supraclavicular, paravertebral, and axillary regions is classic for brown adipose tissue (BAT) activation. Cold exposure activates the sympathetic nervous system, which stimulates BAT metabolism and GLUT-mediated FDG uptake. The patient rested in a cool room, and the distribution is bilateral and characteristic. BAT uptake can be intense and can mimic or mask lymph nodes.
The left cervical node with SUVmax 3.1 is separate from the symmetric BAT pattern, but its uptake could be underestimated or obscured by adjacent BAT. The symmetric uptake should not be called progressive lymphoma without further evaluation. The study should be interpreted with BAT as the likely cause of the symmetric foci, and the cervical node should be correlated with prior imaging, physical examination, and, if needed, a repeat scan under warmed conditions.
2. What patient preparation and imaging steps would you recommend for a repeat study?
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The patient should be prepared in a warm environment, ideally 22–24°C, and should be covered with blankets during the uptake phase. She should avoid cold exposure before injection and while waiting. Fasting and glucose checks should follow the standard protocol. A beta-blocker is not routinely recommended solely to suppress BAT, and it could have clinical effects; warming is the first-line intervention.
For the repeat scan, use the same injected activity, uptake time, and reconstruction as the original study to allow comparison. Review the non-attenuation-corrected images and the maximum-intensity projection to distinguish BAT from nodal disease. If BAT persists despite warming, the report should state that the symmetric uptake is consistent with BAT and that the cervical node should be assessed by clinical correlation or additional imaging. A repeat scan should be scheduled only after adequate warming preparation.