Inclusion Criteria:

• Newly diagnosed (biopsy within 120 days of study enrollment) invasive malignant melanoma of the skin (AJCC 8th edition staging guidelines).
  • pT1b-pT3 (Breslow thickness ≥ 0.8 mm to 4.0 mm) cN0M0; or
  • pT1a (Breslow thickness < 0.8 mm) cN0M0 AND one or more of the following:
    • Mitotic rate ≥ 2/mm2.
    • Patient age at time of primary melanoma biopsy < 40 years old.
    • Presence of lymphovascular invasion.
•  Male or female, age ≥ 18 years.
• Elected to undergo sentinel lymph node biopsy per the treating physician’s recommendation.

Exclusion Criteria:

• Full primary melanoma pathology report unavailable.
• Documented clinically apparent nodal metastases at diagnosis.
• Distant metastatic disease (M1a,b,c,d) clinically present at primary diagnosis.
• Any prior or concurrent primary invasive melanoma mapping to the same draining lymph node basin(s).
• Documented history of another (prior or concurrent) primary invasive melanoma of T1b or greater at any site within the last 5 years.
• Previous surgery in or radiation therapy to the draining lymph node basin(s) of the current primary melanoma.
• Ocular, vulvar, perianal or mucosal melanomas or melanocytic tumors of uncertain malignant potential (MELTUMP) or atypical Spitz tumors.