A 35-year-old man from Mumbai presents with a 2-year history of intermittent diarrhea, abdominal pain, and weight loss (8 kg). He reports a perianal fistula that has been draining for 6 months. Colonoscopy reveals patchy areas of inflammation with intervening normal mucosa in the terminal ileum and colon. Biopsies from an inflamed area show transmural inflammation with non-caseating granulomas in the submucosa. Which of the following pathological findings is MOST consistent with the diagnosis and explains the development of his perianal fistula?