The goal of this observational study is to study blood samples and compare them to other biospecimens and clinical outcomes in participants who have melanoma or non-melanoma skin cancers. The main question it aims to answer is:

• Are blood based signatures able to predict progression-free survival (PFS)?

Participants undergoing regular treatment for their skin cancer will provide blood samples.

This observational study is being done to identify possible biomarkers that can be used for prognostic, prediction, or monitoring considerations in patients with melanoma or non-melanoma skin cancer undergoing treatment. Investigators plan to investigate blood factors which include circulating tumor cells (CTCs - i.e., cancer cells that can be detected in the blood) and their associated protein and mRNA expression; circulating tumor DNA (ctDNA - i.e., pieces of DNA from cancer cells that can be found in the blood); and tumor-derived exosomes (i.e., extracellular vesicles generated by cancer cells that carry nucleic acids, proteins, and metabolites).

Inclusion Criteria:

• Age ≥18 years.
• Participants must meet at least one of the following criteria:
• Finding suspicious of melanoma or non-melanoma skin cancer based on clinical, radiographic, or laboratory findings. Non-melanoma skin cancers include: basal cell carcinoma, cutaneous squamous cell carcinoma, and Merkel cell carcinoma.
• A confirmed diagnosis of melanoma or non-melanoma skin cancer.

Exclusion Criteria:

• Vulnerable populations, including pregnant women, those who lack consent capacity, the mentally ill, prisoners, cognitively impaired persons, children (age <18), and UW employees that report to the investigator(s) or to study team members.
• Not suitable for study participation due to other reasons at the discretion of the investigators.

Participants will be from the Melanoma Medical Oncology Clinic at the Carbone Cancer Center.