A 71-year-old woman comes to the office with a history of headaches, fatigue, and weight loss for 3 months. The headaches are new for her, and usually not very severe. Her jaw also hurts when she is chewing food. Two days prior, she had briefly lost partial vision in her left eye. There were no other neurologic symptoms at the time. On physical examination, her neck is supple to flexion, fundi, and neurologic examinations are normal. She is started on prednisone 60 mg/day and a biopsy is performed to confirm the diagnosis. Which of the following is the most likely change seen on the biopsy to confirm the diagnosis?