Pleuropulmonary blastoma (PPB) is a distinctive, rare primary neoplasm of pleuropulmonary mesenchyme occurring in children. It is virtually always intrathoracic/intrapulmonary. It is categorized into three sub-types (I, II, III), the latter two of which are very aggressive malignancies with metastatic potential. These types are described in detail below. PPB has the unusual biologic features of arising in pre-existing lung cysts and of heralding constitutional/familial disease in 25% of cases . A series of 50 cases has been published by the PPB Registry [Registry Publications, Priest et al, 1997].