The objective of this clinical trial is to determine whether a Photoacoustic flow cytometry (PAFC)-based prototype device can detect circulating tumor cells (CTCs) in the blood of melanoma patients in vivo, in real time, and do so at detection limits at least one order of magnitude below the detection limits of currently existing ex vivo methods.

Study Population: Approximately 80 subjects will be consented in order to achieve an enrollment goal of 75 subjects at this institution in three cohorts as follows:

1. Cohort #1 will consist of fifteen healthy control subjects, ten of whom will be Caucasian and five of whom will be African-American. Subjects in cohort #1 will be used to address the calibration goal of Specific Aim #1.
2. Cohort #2 will consist of 30 subjects who have advanced-stage melanoma will be recruited from the Medical Oncology clinic at UAMS, where advanced stages are defined as Stages III or IV. Subjects in cohort #2 will be used to address the validation goal of Specific Aim #2. Approximately half of the 30 advanced-stage subjects will be Stage III and the other half will be Stage IV.
3. Cohort #3 will consist of 30 subjects with early-stage melanoma will be recruited from the Surgical Oncology clinic at UAMS, where early stages are defined as Stages I or II.

Subjects in cohort #3 will be used to address the detection goal of Specific Aim #3. Approximately 10 of the 30 early-stage subjects will be Stage I and approximately 20 will be Stage II.

Inclusion Criteria:

• Age 18 to 80 years
• Histological documented diagnosis of melanoma
• Signed informed consent form approved by the University of Arkansas for Medical Sciences (UAMS) Institutional Review Board (IRB)
• Must be able to sit still for 90 minutes

Exclusion Criteria:

• Active infection
• Current and significant medical or surgical condition as determined by the Investigator
• Diagnosis or evidence of organic brain syndrome
• Pregnancy or breastfeeding

Expect to consent approximately 80 subjects in order to achieve an enrollment goal of 75 subjects at this institution in three cohorts.