A 72-year-old man with a history of chronic sun exposure presents with a 1.2 cm erythematous, scaly plaque on the left ear helix that has been growing for 6 months. On examination, the lesion is firm, with indistinct borders and surrounding solar elastosis. There is a single firm, mobile lymph node (1.5 cm) in the ipsilateral cervical region. Biopsy confirms moderately differentiated squamous cell carcinoma with invasion into the reticular dermis. Which of the following is the most appropriate next step in management?