Incidental Detection of Metastatic Malignant Melanoma on 68Ga-Prostate-Specific Membrane Antigen PET/CT Imaging: Correlative Imaging With FDG PET/CT and Review of the Literature.

An 80-year-old man with suspected recurrent prostate carcinoma underwent Ga-68-PSMA PET/CT, which showed enlarged axillary lymph nodes with intensely increased Ga-68-PSMA uptake, an atypical site for prostate cancer metastasis. Fine-needle aspiration biopsy revealed metastatic malignant melanoma. FDG PET/CT revealed congruent intense FDG uptake. Therefore, malignant melanoma should be included in the list of malignancies that can be seen positive on Ga-68-PSMA PET/CT. In unclear Ga-68-PSMA PET-positive lesions, further clarification with other imaging techniques or biopsy is mandatory to avoid scan misinterpretation. Review of the literature revealed other non-prostate cancer causes of elevated PSMA uptake classified into neoplastic and nonneoplastic conditions.