Which microscopic findings are characteristic of acute cellular lung transplantation rejection, grade A?

Updated: Jun 06, 2019
  • Author: Aliya N Husain, MBBS, MD; Chief Editor: Philip T Cagle, MD  more...
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Perivascular inflammation forms the basis of grade A acute cellular rejection. The cellular components are the same in each of the following grades, which are determined by the extent of the inflammatory infiltrate:

  • Grade AX: No alveolated lung tissue or no arteriole or venule, precluding determination of the presence or absence of perivascular infiltrates

  • Grade A0 (no acute rejection): Normal pulmonary parenchyma without perivascular inflammation

  • Grade A1 (minimal acute rejection): Scattered perivascular infiltrates forming an incomplete or a two- or three-cell–layer–thick cuff (see the following image); rare eosinophils may be seen; endothelialitis is usually absent

    Lung transplantation-related pathology. This image Lung transplantation-related pathology. This image depicts minimal acute cellular rejection with incomplete perivascular cuff of inflammatory cells (grade A1) (hematoxylin and eosin [H&E], 200x).


  • Grade A2 (mild acute rejection): More frequent perivascular infiltrates (may be densely compacted or loose) consisting of round lymphocytes, activated lymphocytes, plasmacytoid lymphocytes, and macrophages (see the image below); eosinophils and endothelialitis may be present

    Lung transplantation-related pathology. This image Lung transplantation-related pathology. This image shows mild acute perivascular rejection with a thick complete cuff around a blood vessel (grade A2) (hematoxylin and eosin [H&E], 200x).


  • Grade A3 (moderate acute rejection): Dense perivascular mononuclear cell infiltrates with frequent foci of endothelialitis and extension into alveolar walls (see the following image); eosinophils and neutrophils are frequently present

    Lung transplantation-related pathology. Moderate a Lung transplantation-related pathology. Moderate acute perivascular rejection is revealed: The inflammation extends into adjacent alveolar walls and is accompanied by fibrinous exudates (grade A3) (hematoxylin and eosin [H&E], 200x).


  • Grade A4 (severe acute rejection): Diffuse perivascular, interstitial and alveolar infiltrates of mononuclear inflammatory cells; prominent pneumocyte damage and endothelialitis; intraalveolar necrotic epithelial cells, hyaline membranes, hemorrhage, and neutrophils may be seen

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