This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Which of the following is a stain for heart failure cells? \nSelect and explain. \nA. PAS, B. Prussian blue, C. Sudan black, D. Oil red', 'role': 'user'}, {'content': "Answer: B \nExplanation: 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.\nHemosiderin is nothing else but stored iron granules.\nSo, heart failure cells contain iron granules and thus will require a stain that is used for iron.\nStain used for iron is Prussian blue reaction (Perl's iron stain)", 'role': 'assistant'}]