The term desquamative interstitial pneumonia (DIP)-like pattern describes the accumulation of macrophages in the alveoli that can take place as a nonspecific reaction adjacent to a variety of lesions, the most classic example being pulmonary Langerhans cell histiocytosis (see Chapter 29). Many of these cases of DIP-like reaction represent respiratory bronchiolitis-associated interstitial lung disease (see Chapter 80). However, a DIP-like reaction can be seen in and around localized parenchymal masses and interstitial fibrosis in the lung. DIP-like reactions can be seen with usual interstitial pneumonia, nonspecific interstitial pneumonia, asbestosis, human immunodeficiency virus infection, drug reactions, scars, tumors, and infarcts.