Pulmonary blastoma: an ultrastructural study with a brief review of literature and a discussion of pathogenesis.

A pulmonary blastoma is reported in a 19-year-old black female. The light and electron microscopic characterics are described; they are found to be similar to those of the fetal lung prior to the fourth gestational month. Although the ultrastructural features do not favor any particular theory of histogenesis of this unique tumor, evidence for the commonly held theory that the tumor arises from pluipotential pulmonary blastema seems tenuous. A brief review of the literature disclosed 38 other similar cases. There was a male predominance with an average age of detection at 39 years. Sputum cytology was rarely positive. Among tumors larger than 5 cm in diameter, survival was usually less than 2 years. Metastases were present in approximately half of the cases.