Divergent Radiomolecular Phenotype of Spindle Cell Lipoma

A 68-year-old man with gastric cancer underwent 18F-fluorodeoxyglucose (FDG) PET/CT, which revealed an incidental subcutaneous lesion suspicious for low-grade sarcoma or metastasis. The patient initially declined a biopsy. One month later, following a new diagnosis of prostate cancer, 68Ga-prostate-specific membrane antigen (PSMA) PET/CT was performed. The unchanged lesion demonstrated heterogeneous, moderate PSMA uptake. Subsequent histopathologic examination confirmed the lesion as a spindle cell lipoma. In conclusion, spindle cell lipomas can exhibit mild 18F-FDG and moderate PSMA uptake, serving as a potential pitfall that can mimic malignancy and cause false-positive results in oncologic PET/CT imaging.