A Study on How to Safely Guide Surgery for Melanoma and Similar Skin Tumors in Children Using Pathology and Genetic Information

Inclusion Criteria: * Patients ≤ 25 years old * Newly diagnosed localized cutaneous melanoma, atypical Spitz/Spitzoid tumors, or other atypical melanocytic neoplasm by local institution pathology report * Patients must have disease that is localized to the skin on clinical assessment. Note that staging imaging is not required for the determination of eligibility, but if obtained prior to enrollment, all imaging must be consistent with localized cutaneous disease * Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1 or 2. Use Karnofsky for patients \> 16 years of age and Lansky for patients ≤ 16 years of age * Patients must not have received any prior chemotherapy, immunotherapy, targeted therapy, radiation, or surgical therapy for melanoma other than the permitted biopsy/excision of the lesion for which they are enrolling. Note that prior biopsies/surgery for other benign melanocytic lesions is permitted Exclusion Criteria: * Patients ≥ 18 years old with conventional adult-type melanoma are excluded. Note that patients 18-25 years old with atypical Spitz/Spitzoid tumors, or other atypical melanocytic neoplasms are eligible * Patients with clinical evidence of metastatic disease such as palpable malignant adenopathy or symptomatic distant metastases are not eligible * Patients who have undergone re-excision to achieve a negative margin or sentinel lymph node biopsy for the melanocytic neoplasm under study are not eligible. Note that this does not exclude patients who have undergone the permitted diagnostic biopsy/excision, including re-biopsy, of the lesion * Any of the following diagnoses * Congenital nevi-associated proliferative nodules * Agminated Spitz nevi/tumors * Dysplastic nevus * Combined nevus * CRTC1::TRIM11 and/or MED15::ATF1 fused tumors (molecular testing is not required prior to enrollment) * Pre-existing conditions: * Solid organ transplant recipients * Known melanoma predisposition syndrome (i.e., patients with previously known pathogenic variants in moderate and high penetrance melanoma susceptibility genes \[i.e., CDKN2A, CDK4, BAP1, POT1, TERT promoter, ACD, TERF2IP\] or Xeroderma Pigmentosum). Note germline testing is not required prior to enrollment * All patients and/or their parents or legal guardians must sign a written informed consent * All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met