Pleuropulmonary blastoma

Pleuropulmonary blastoma (PPB) is a rare pediatric tumor of the lung that arises during fetal lung development and is often part of an inherited cancer syndrome ({5:Hill et al., 2009}). PPBs contain both epithelial and mesenchymal cells. Early in tumorigenesis, cysts form in lung airspaces, and these cysts are lined with benign-appearing epithelium. Mesenchymal cells susceptible to malignant transformation reside within the cyst walls and form a dense 'cambium' layer beneath the epithelial lining. In a subset of patients, overgrowth of the mesenchymal cells produces a sarcoma, a transition that is associated with a poorer prognosis ({6:Priest et al., 1996}). In approximately 35% of families in which a child has PPB, the patient or a family member manifests 1 or more additional conditions from an unusual array of dysontogenetic-dysplastic and malignant conditions, known as the 'PPB family tumor and dysplasia syndrome' (PPBFTDS). Cystic nephroma, which are benign lesions of the kidney, are found in 9 to 10% of family members affected by PPB (summary by {1:Bahubeshi et al., 2010}). Larger studies have shown that DICER1 mutations are associated with a variety of tumor types, indicating that this disorder can be considered a tumor predisposition syndrome (summary by {7:Slade et al., 2011}).