Radiation therapy-induced phrenic neuropathy mimicking metastasis to the diaphragmatic crus on ¹⁸F-FDG PET/CT.

Benign unilateral uptake in the diaphragmatic crus is a relatively uncommon finding on (18)F-FDG PET/CT that can mimic the appearance of malignancy in patients with known cancer, as illustrated in this patient with neuroendocrine carcinoma. It is important for the PET interpreter to recognize this finding and attribute it to benign uptake based on the patient's history and symptoms at the time of the scan. Correlation with the findings of other available imaging modalities is also important to characterize focal uptake in unusual locations.