BACKGROUND: Pitfalls in Fluorine 18 Positron Emission Tomography Computed Tomography (18F FDG PET-CT) could mislead an appropriate treatment plan by an inexperienced PET reader.

METHODS: An incidental finding of a false-positive FDG-avid fatty lesion in the right gluteal region was observed on PET-CT evaluation performed for post-treatment non-small cell lung carcinoma (NSCLC) in a 40-year-old man. Post-treatment monitoring with 18F FDG PET-CT revealed partial remission of the right upper lobe mass, progressive metabolic activity in mediastinal lymphadenopathy, and new metastatic lesions in the left upper lobe and at the T12 vertebra. There was also increased FDG-avidity in the previously noted right gluteal fatty lesion, raising suspicion for metastasis.

RESULTS: A biopsy of the right gluteal lesion confirmed a hibernoma. The patient opted for conservative management with maintenance chemotherapy (erlotinib 150 mg once daily).

CONCLUSION: Pitfalls in 18F FDG PET-CT interpretation may mislead treatment decisions in cancer patients. Careful characterization of benign versus malignant lesions is essential to avoid inappropriate therapy.

KEYWORDS: hibernoma; 18F FDG PET-CT; gluteal region; lung carcinoma; NSCLC