V.2.2. Cytology & Pathology
From a pathophysiological viewpoint, direct evidence of an eosinophilic type 2 inflammation associated with and attributed to a fungus is compelling evidence for ongoing fungal allergic disease. Direct microscopic examination of naso-sinusal, bronchial, or sputum samples may be performed in search of eosinophilic inflammation with fungal non-invasive colonization of thick mucus plugs (89). Eosinophils, eosinophilic inflammation markers such as Charcot-Leyden crystals, and fungal hyphae were recently proposed as pathognomonic for ABPA/ABPM (88).