A 52-year-old man from Rajasthan presents with a 6-month history of progressive weight loss, night sweats, and productive cough with blood-tinged sputum. On examination, he is cachectic with crackles in the right upper lobe. Chest X-ray shows a cavitary lesion in the right upper lobe with surrounding consolidation. Sputum smear microscopy is positive for acid-fast bacilli (AFB). A lung biopsy from the cavity wall shows caseating granulomas with central caseous necrosis surrounded by epithelioid cells and lymphocytes. What is the histological significance of the caseous necrosis in this lesion?