CASE PRESENTATION: A 53 year old woman was admitted to hospital for further evaluation of mediastinal widening and ground-glass opacities on her CT. These abnormalities had first been noticed 1 month previously, when she got a cold and felt a bit out of breath. In addition to mild short of breath, she had no other complains. Her vital signs are stable, she had no positive signs, except for some crackles in the bottom of the lung. CT showed diffuse soft tissue infiltration in the mediastinum without displacement of the vessels. Patchy bilateral ground-glass opacities and bilateral smooth thickening of the interlobular septa and bronchovascular bundles were observed in the lung parenchyma. Bronchoscopy showed mucosal inflammation with congestive and edema of the mucosa, The tracheal carina was sharp during inspiratory phase, while was blunt during expiratory phase. The airway wall was also the same. Pulmonary and mediastinal biopsies were taken by means of video-assisted thoracoscopy and mediastinoscopy. Pathological examination showed an increase in the number of lymphatic channels in the lung parenchyma, lined by flattened endothelial cells strongly positive for CD31 on immunohistochemical study. Fibrous tissue components were observed in the Mediastinal lymph nodes. The pathology leading to the definitive diagnosis of DPL.