Siderophage

Heart failure cells are siderophages generated in the alveoli of the lungs of people with left heart failure or chronic pulmonary edema, when the high pulmonary blood pressure causes red blood cells to pass through the vascular wall.

They are present wherever red blood cells encounter macrophages, such as pulmonary hemorrhage.

The resulting backup causes increased pressure on the alveolar capillaries, and red blood cells leak out.

Alveolar macrophages (dust cells) engulf the red blood cells, and become engorged with brownish hemosiderin.

In chronic pulmonary edema, alveolar septa become thick and fibrous, again increasing pressure on alveolar capillaries and resulting in leakage of red blood cells which undergo phagocytosis by alveolar macrophages.