Bronchoalveolar lavage (BAL) usefully provides specimens for cytological examination, microbial cultures, and molecular analysis. Besides infections, BAL can be of diagnostic value in several situations. In the context of pulmonary alveolar proteinosis, BAL abnormalities are characterized by milky appearance fluid, abundant proteinaceous periodic acid schiff positive material, and presence of foamy alveolar macrophages (AM) [70] . BAL can also be diagnostic for pulmonary alveolar haemorrhage [11] . This diagnostic is easy when the BAL fluid has a bloody or pink color, but its gross appearance may be normal. Microscopic analysis may then be of value by documenting the presence of red blood cells in AM or haemosiderin laden AM [71] . Among other situations, the diagnosis of Langerhans cell histiocytosis can be performed with the use of the monoclonal antibodies revealing the presence of CD1a positive cells (in more than 5% of the BAL cells) [72] . Lipid disorders with lung involvement represent another indication of BAL. This includes congenital lipid-storage diseases (Gaucher's disease and Niemann-Pick disease) or chronic lipid pneumonia due to chronic aspiration [73, 74] . However, in cases of aspiration syndromes, the presence of lipid laden AM is sensitive but not specific [75] .