Benign or malignant: FDG-avid splenic lesion in a patient with melanoma

Though hypermetabolic metastatic splenic lesions have been reported in patients with melanoma on fluorine 18-fluorodeoxyglucose (FDG) PET-CT, FDG-avid benign splenic lesions in known cases of melanoma are exceedingly rare. These lesions can cause diagnostic confusion and potentially lead to inadvertent interventional or surgical procedures. An 82-year-old patient with a history of scalp melanoma was found to have an isolated FDG-avid splenic lesion. While it was initially diagnosed as splenic metastases on a PET-CT, it was later confirmed to be a splenic infarct secondary to an episode of bacterial endocarditis. The objective of this case report is to highlight the diagnostic dilemma posed by hypermetabolic splenic lesions in the setting of a known malignancy. This case reports emphasizes the importance of carefully considering patients' clinical history, laboratory findings, and other noteworthy differentials for hypermetabolic lesions before undertaking invasive procedures.