A 30-year-old man is evaluated for persistent cough, night sweats, low-grade fever, and general malaise. A chest X-ray reveals findings "consistent with a Ghon complex." Sputum cultures grow acid-fast bacilli. Examination of hilar lymph nodes in this patient would most likely demonstrate which of the following pathologic changes?

The answer is A: Caseous necrosis. Grossly, necrosis in tuberculosis has a granular, cheesy appearance and is therefore called caseous necrosis. Microscopically, this necrotic material appears as amorphous, structureless, eosinophilic, granular debris, with complete loss of cellular details (as opposed to coagulative necrosis, in which cell outlines are preserved). Fibrinoid necrosis (choice D) is seen in patients with necrotizing vasculitis.