A 52-year-old Indian man presents with a pigmented lesion on his left sole that has been slowly enlarging over 8 months. Dermoscopy shows irregular borders, variegated brown-black coloration, and diameter of 9 mm. Excision biopsy confirms the diagnosis shown as **C** in the diagram. Histopathology reveals tumor cells extending 2.8 mm vertically from the granular layer to the deepest invasive component. Which of the following is the MOST appropriate next step in management?