A 58-year-old man with fair skin presents for evaluation of a changing mole on his upper back. He reports the lesion has enlarged over the past 6 months and occasionally bleeds after showering. He has a history of multiple blistering sunburns in adolescence. Physical examination shows a 1.3-cm asymmetric pigmented lesion with irregular borders and variegated color (tan, dark brown, and black). Dermoscopy demonstrates atypical pigment network and irregular streaks. An excisional biopsy confirms melanoma. Which of the following is the most appropriate next step in management to reduce the risk of local recurrence?

(Assume no evidence of distant metastasis on initial evaluation.)