Background:
Fluorodeoxyglucose positron emission tomography (FDG-PET) is central to staging and surveillance in malignant melanoma. Although FDG uptake is typically associated with malignancy, a range of benign conditions may also demonstrate avidity, creating diagnostic uncertainty and risk of overstaging. Recognition of these mimics is essential to avoid unnecessary intervention and inappropriate management.
Methods:
We describe a case of a patient with high-risk melanoma in whom staging PET-CT demonstrated numerous FDG-avid subcutaneous lesions concerning for disseminated metastatic disease. Clinical history, imaging findings, and histopathological correlation were reviewed.
Results:
A 71-year-old woman with pT4a melanoma (Breslow depth 9 mm) underwent staging PET-CT, which demonstrated avidity at the primary site, a cervical lymph node, and numerous mildly FDG-avid subcutaneous nodules suspicious for widespread cutaneous metastases. The patient reported these nodules had been present for many years. Excision biopsy of a representative lesion confirmed a benign angiolipoma. In the context of longstanding lesions and benign histology, further biopsy was avoided and the additional nodules were presumed benign. The patient proceeded to definitive surgical management (final stage IIIC) and adjuvant immunotherapy.
Conclusion:
FDG avidity is not specific for malignancy. Benign lesions such as angiolipomas may closely mimic metastatic melanoma, particularly when multiple. Correlation with clinical history and selective biopsy of representative lesions are critical to prevent misdiagnosis, unnecessary procedures, and inappropriate upstaging. Awareness of PET-avid benign mimics is essential for accurate melanoma staging and optimal patient management.