What is included in the histologic exam to evaluate lung transplant rejection?

Updated: Jun 06, 2019
  • Author: Aliya N Husain, MBBS, MD; Chief Editor: Philip T Cagle, MD  more...
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Given the patchy nature of rejection, a consensus statement by the Lung Rejection Study Group (LRSG) recommends five fragments of well-expanded alveolated lung (with bronchioles and >100 alveolar spaces) be examined. [4] This may require more than five transbronchial biopsies, especially to recognize features of bronchiolitis obliterans (BO). Specimens may be gently agitated in formalin to inflate the fragments but require sensitive handling to avoid crush artifacts.

Histologic examination should include sections from three levels of the paraffin block for hematoxylin and eosin (H&E) staining. Connective-tissue stains may help evaluate any submucosal fibrosis. Silver stains can be performed for fungi. Immunohistochemical stain for cytomegalovirus (CMV) is very helpful and strongly recommended. Concomitant bronchoalveolar lavage (BAL) fluid may be analyzed to exclude infection, but it plays no role in the diagnosis of rejection.

If the biopsy samples contain diagnostic material but do not meet the minimum assessable criteria, grading should be carried out as usual, with a comment describing the number of lung fragments and emphasis that the material may not be representative of the overall allograft. Similarly, if no alveolated lung or no airway is present, the type of rejection should be indicated by the appropriate letter, suffixed by an "X" (see below). Biopsies taken for rejection surveillance should always be evaluated for histopathologic features indicative of infection, aspiration, organizing pneumonia, recurrent disease (eg, sarcoidosis), and PTLD.

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