Interestingly, while pulmonary blastomas with well-differentiated fetal adenocarcinoma as the epithelial component are a clearly defined group, (13) tumors with a high-grade carcinomatous component are distinct from it.
Another pitfall is the presence of squamous morules (Figure 4, D), which again are of lower grade than the associated adenocarcinoma, for example, in [beta]-catenin-positive, well-differentiated fetal adenocarcinoma.
[Clear cell adenocarcinoma with a component of
well-differentiated fetal adenocarcinoma; report of a case] Kyobu Geka 2006;59:867-70.
The differential diagnostic clinical and pathologic features of pulmonary blastoma versus
well-differentiated fetal adenocarcinoma and pleuropulmonary blastoma are summarized in Table 2.
The presence of malignant stroma is the primary feature distinguishing pulmonary blastoma from
well-differentiated fetal adenocarcinoma. The most common, and possibly most difficult, problem in the differential diagnosis is with malignant mesothelioma.