A rare pediatric pulmonary blastoma that arises during fetal lung development and is often part of an inherited cancer syndrome. Tumors contain both EPITHELIAL CELLS and mesenchymal cells and arise from cysts in the lung airspace epithelium. In some patients, overgrowth of the mesenchymal cells produces a SARCOMA, which is associated with a poorer prognosis. Germline mutations in the DICER1 gene have been identified. OMIM: 601200
