Basophilic staining in pulmonary alveolar proteinosis. Report of three cases

Material filling the alveoli in pulmonary alveolar proteinosis has been shown to be eosinophilic by hematoxylin-eosin (HE) staining of lung tissue. No previous evidence has suggested a different result from a frozen section. We noted three cases, in 1972, 1973, and 1982, of basophilic staining of this characteristic alveolar material on unfixed, frozen sections; these cases later showed the usual eosinophilic properties when HE staining was performed at room temperature on formaldehyde solution-fixed, paraffin-embedded sections. These observations are important in that failure to recognize this possibility may initially lead the surgical pathologist away from the correct diagnosis or falsely suggest a problem in stains or staining techniques.