This is a monocentric prospective study. This study aims to investigate the prognostic value of the novel melanin-targeted imaging modality 18F-PFPN PET in patients with melanoma and seek independent prognostic factors for progression-free survival (PFS) and overall survival (OS). The patients with clinically highly suspected or confirmed melanoma who underwent 18F-PFPN and 18F-FDG PET scans will be enrolled consecutively. Patients' PET images, clinical characteristics, and follow-up information will be collected for prognostic analyses. This study plans to set the sample size as 100 cases.

Melanoma is an aggressive malignancy with a high mortality rate. Accurate diagnosis and prognostic risk assessment are essential to the clinical management of melanoma. Melanin is present in most melanoma and has become a potential target for melanoma. This team has successfully synthesized a positron nuclide targeting melanin probe named 18F-PFPN (18F-N-(2-diethylaminoethyl)-4-(2-[2-ethoxy]-ethoxy) pyridine), which has been proven to be safe and well-tolerated. It has shown excellent diagnostic value in both primary and metastatic melanoma. This prospective study was designed to further investigate the prognostic value of 18F-PFPN for melanoma and compare it with the general metabolic imaging agent 18F-FDG. In this study, patients with clinically highly suspected or confirmed melanoma who underwent 18F-PFPN and 18F-FDG PET scans will be enrolled consecutively. Patients' PET images, clinical characteristics, and follow-up information will be collected for prognostic analyses.

Inclusion Criteria:

• Patients with histopathologically confirmed melanoma;
• Patients with complete clinical and follow-up data (including TNM stage, subtypes, and treatment strategies).

Exclusion Criteria:

• Uncertain histopathology;
• A history of other malignancies.

Patients with clinically highly suspected or confirmed melanoma underwent 18F-PFPN and 18F-FDG PET scans in the PET center.