Acute fibrinous and organizing pneumonia: two case reports and literature review.

Background: Acute fibrinous and organizing pneumonia (AFOP) is a very rare form of acute or subacute lung injury, which is characterized by patches of "fibrin balls" distributed within the alveoli. Given the lack of typical clinical manifestations, AFOP is often misdiagnosed as pneumonia, tuberculosis, etc. Definitive diagnosis is obtained from a lung biopsy.