Prostate-Specific Membrane Antigen-Avid Neurofibroma Mimicking Cutaneous Metastasis in Metastatic Castration-Resistant Prostate Cancer on 18F-PSMA-1007 PET/CT.

The occurrence of cutaneous metastases in prostate cancer is exceedingly rare. Many benign lesions and nonprostatic cancers can express the prostate-specific membrane antigen (PSMA). They can potentially mimic metastasis of prostate cancer and lead to misinterpretation of PSMA PET/CT findings. Additionally, it has significant management and prognostic implications. We present a rare case of an 88-year-old man with metastatic castration-resistant prostate cancer who showed a PSMA-expressing subcutaneous nodule in the scalp on 18F-PSMA-1007 PET/CT, raising the suspicion of cutaneous metastasis. However, its biopsy revealed a neurofibroma, altering the disease prognosis and management.