Bronchovascular structures in the central part of the upper lobe are normal, but more peripherally, the arrow indicates an ectatic airway. Most of the central parenchyma in the upper lobe is mildly emphysematous compared to that in the lower lobe. The emphysema, bronchiectasis, and presumed bronchiolar disease all contribute to airflow obstruction. The caseous material is friable and white. There was no evidence of active disease in this patient, although dormant bacilli are undoubtedly present in the caseous material.
Caseous necrosis refers to necrosis that has a crumbly, white, cheesy appearance.
The term should be restricted to the gross appearance in tuberculosis. Nevertheless, this appearance is not specific for tuberculosis and can occur in fungal diseases, sarcoidosis, Wegener's granulomatosis, and neoplasms. Histologically, the material should be described as necrotic, rather than caseous. Similarly, the term tubercle should be reserved for the granuloma of tuberculosis. Two thin-walled cavities are shown here.