A, B, Photomicrographs showing lipoproteinaceous material filling alveolar spaces with positive periodic acid-Schiff results (A, ×200; B, ×400). C, Electron microscopic image showing BAL fluid exhibiting whorled membranous structures and amorphous osmiophilic particles. D, Higher magnification electron microscopic image showing a whorled membranous body with concentric osmiophilic membranes resembling tubular myelin.