Airway Pathology in Lung Transplants

The histologic diagnosis of lung transplant rejection is based on the assessment of perivascular mononuclear cell inflammation, airway inflammation and fibrosis, and vasculopathic changes. This chapter describes the pathologic features of acute and chronic rejection of the small airways (i.e., lymphocytic and obliterative bronchiolitis). As transbronchial lung biopsy is the mainstay for the assessment of rejection, a brief discussion of some of the limitations of this technique is provided from the pathologist’s perspective. Several important and common entities that can mimic airway rejection are described with practical guidance for distinguishing these potential confounders on transbronchial biopsy. The non-rejection findings that are discussed include the normal biopsy, nonspecific forms of chronic bronchiolitis, cytomegalovirus and pneumocystis pneumonia, bronchiolitis obliterans-organizing pneumonia, and aspiration pneumonia.