Pulmonary blastoma evolving into carcinosarcoma

A rare lung tumor composed of contiguous foci of classical blastoma and carcinosarcoma with transitional features is described. Based on these observations and a review of the literature, we propose that pulmonary carcinosarcomas are composed of a heterogeneous population of tumors. This case supports the concept that blastomas are a distinctive subtype of carcinosarcomas. An unusual feature in the clinical presentation was the expectoration of an endobronchial portion of tumor.