<prompt> Which of the following is a stain for heart failure cells?PASPrussian blueSudan blackOil red  <response>: Heart failure cells, also called siderophages, are hemosiderin-containing macrophages in the alveoli of lung and these cell denote previous episodes of pulmonary edema due to left-sided heart failure.Hemosiderin is nothing else but stored iron granules.So, heart failure cells contain iron granules and thus will require a stain that is used for iron.Stain used for iron is Prussian blue reaction Perls iron stain 