Pulmonary infarction and pulmonary edema is differentiated by-

Pulmonary edema & pulmonary infarction can be differentiated by the presence of heart failure cells in pulmonary edema. Whatever is the clinical setting, pulmonary congestion & edema are characterized by heavy, wet lungs. Fluid accumulates initially in the basal regions of the lower lobes because hydrostatic pressure is greater in these sites. Histologically the alveolar capillaries are engorged, & an intraalveolar granular pink precipitate is seen. Alveolar microhemorrhages & hemosiderin laden macrophages called Heart Failure Cells may be seen. In long-standing cases of pulmonary congestion, such as those seen in mitral stenosis, hemosiderin-laden macrophages are abundant, and fibrosis and thickening of the alveolar walls cause the soggy lungs to become firm and brown (brown induration).