[Pulmonary blastoma: a light-microscopic, immunohistochemical and electron-microscopic study of six cases in childhood].

Pulmonary blastoma is a very rare primary tumor of the lung, which mostly occur at a late age in adults. Six cases in children under four years of age are reported in this series. The light-microscopic, immunohistochemical and electron-microscopic characteristics revealed that the elements of P.B. in childhood consist mainly of mesenchymal components, including undifferentiated large cells and small round cells, which tend to differentiate toward rhabdomyosarcoma. The epithelial components comprise only a small portion of the total tumor, and most appear as the well-demarcate branching tubular structures lined with columnar or cubiodal epithelium merging with the stroma. The degree of differentiation of mesenchymal elements is closely related to the prognosis.