If a small biopsy specimen shows only a fetal adenocarcinoma pattern, one cannot exclude the possibility of a biphasic pulmonary blastoma, realizing the blastematous component may not have been sampled.
68,69) Natatani et al (68) found mutations in exon 3 of the [beta]-catenin gene in 3 of 4 blastomas, but not in 5 carcinosarcomas with a high-grade fetal adenocarcinoma component.
The differential diagnostic clinical and pathologic features of pulmonary blastoma versus well-differentiated fetal adenocarcinoma and pleuropulmonary blastoma are summarized in Table 2.
7 The final subtype, pulmonary blastoma, is a biphasic tumor composed of a primitive epithelial component resembling well-differentiated, fetal adenocarcinoma and a primitive mesenchymal stroma that may contain rhabdomyosarcoma, osteosarcoma, or chondrosarcoma (Figure 2, F).
The presence of malignant stroma is the primary feature distinguishing pulmonary blastoma from well-differentiated fetal adenocarcinoma.