Pleuropulmonary blastoma is THE pulmonary blastoma of childhood.

Pulmonary blastoma was defined by Spencer and others as a neoplasm with histopathological features thought to be reminiscent of Wilms' tumor. Unlike the other embryonal-fetal neoplasms that typically occur in early childhood, the majority of pulmonary blastomas have been reported in adults. One explanation offered by Spencer for the delayed clinical presentation of pulmonary blastoma is the continued development of lung parenchyma well past the postnatal period. It has been proposed that the pulmonary blastoma is a variant of carcinosarcoma, which is seen almost exclusively in adults. The classic pulmonary blastoma is described as a neoplasm with a mixture of primitive tubular profiles, immature blastema, and a spindle cell stroma. More recently, some have included the well-differentiated adenocarcinoma of fetal type as a pure epithelial expression of pulmonary blastoma. By contrast, most cases of pulmonary blastoma in children have been described as having an exclusive mesenchymal composition, either embryonal rhabdomyosarcoma or a complex, mixed blastematous and sarcomatous neoplasm. Some pulmonary blastomas in children, particularly those with only embryonal rhabdomyosarcoma, have presented as a peripheral multicystic lesion that has been interpreted as a developmental cyst, either cystic adenomatoid malformation or bronchogenic cyst. Other tumors have been described as intrathoracic and anatomically separate from the lung, like some extralobar sequestrations. We have proposed the designation pleuropulmonary blastoma for these pulmonary or extrapulmonary neoplasms of childhood. We propose that this neoplasm is the rightful pulmonary blastoma rather than the pulmonary blastoma of Spencer, which has been the long-time pretender to the title.