Organizing pneumonia

Organizing pneumonia (OP) refers to a clinicopathological entity which is associated with non-specific clinical findings, radiographic findings, and pulmonary function test results.

When an underlying cause is unknown it is classified as cryptogenic organizing pneumonia (COP; also referred to as primary organizing pneumonia) whereas if a cause is known it is then termed a secondary organizing pneumonia.


Most cases of organizing pneumonia (50-70%) are classified as cryptogenic .


Microscopic appearance

Organizing pneumonia comprises a histological pattern characterized by granulation tissue polyps within alveolar ducts and alveoli and with chronic inflammation involving the adjacent lung parenchyma. ​

Treatment and prognosis

Most (especially cryptogenic forms) respond very well to corticosteroid treatment; however, a small percentage of patients many develop progressive fibrosis -  fibrosing organizing pneumonia .