MelmarT Melanoma Margins Trial Investigating 1cm v 2cm Wide Excision Margins for Primary Cutaneous Melanoma

Inclusion Criteria: 1. Patients must have a primary invasive cutaneous melanoma of Breslow thickness greater than 1 millimetre as determined by diagnostic biopsy (narrow excision, incision or punch biopsy) and subsequent histopathological analysis. 2. Patients must have had the invasive primary completely excised, including any in situ component but excluding melanocytic atypia, with a narrow margin, either in one stage or more than one stage in the case where an incision or punch biopsy has previously been performed. This information, including measured margins of lateral and deep clearance must be documented on the pathology report. 3. Must have a primary melanoma that is cutaneous (including head, neck, trunk, extremity, scalp, palm, sole). 4. An uninterrupted 2cm margin must be technically feasible around biopsy scar or primary melanoma. 5. Randomisation and the primary study intervention, including staging sentinel node biopsy, must be completed by 120 days of original diagnosis. 6. Patients must be 18 years or older at time of consent. 7. Patient must be able to give informed consent and comply with the treatment protocol and follow-up plan. 8. Life expectancy of at least 10 years from the time of diagnosis, not considering the melanoma in question, as determined by the PI. 9. Patients must have an ECOG performance score between 0 and 1. 10. A survivor of prior cancer is eligible provided that ALL of the following criteria are met and documented: * The patient has undergone potentially curative therapy for all prior malignancies, * There has been no evidence of recurrence of any prior malignancies for at least FIVE years (except for successfully treated cervical or non-melanoma skin cancer with no evidence of recurrence), and * The patient is deemed by their treating physician to be at low risk of recurrence from previous malignancies. Exclusion Criteria: 1. Uncertain diagnosis of melanoma i.e. so-called 'melanocytic lesion of unknown malignant potential'. 2. Patient has already undergone wide local excision at the site of the primary index lesion. 3. Patient unable or ineligible to undergo staging sentinel lymph node biopsy of the primary index lesion. 4. Desmoplastic or neurotropic melanoma. 5. Microsatellitosis as per AJCC 2009 definition 6. Subungual melanoma 7. Patient has already undergone a local flap reconstruction of the defect after excision of the primary and determination of an accurate excision margin is impossible. 8. History of previous or concurrent (i.e., second primary) invasive melanoma. 9. Melanoma located distal to the metacarpophalangeal joint, on the tip of the nose, the eyelids or on the ear, mucous membranes or internal viscera. 10. Physical, clinical, radiographic or pathologic evidence of satellite, in-transit, regional, or distant metastatic melanoma. 11. Patient has undergone surgery on a separate occasion to clear the lymph nodes of the probable draining lymphatic field, including sentinel lymph node biopsy, of the index melanoma. 12. Any additional solid tumour or hematologic malignancy during the past 5 years except T1 skin lesions of squamous cell carcinoma, basal cell carcinoma, or uterine/cervical cancer. 13. Melanoma-related operative procedures not corresponding to criteria described in the protocol. 14. Planned adjuvant radiotherapy to the primary melanoma site after Wide Local Excision is not permitted as part of the protocol and any patients given this treatment would be excluded from the study. 15. History of organ transplantation. 16. Oral or parenteral immunosuppressive agents (not topical or inhaled steroids) at any time during study participation or within 6 months prior to enrolment.