Pulmonary blastoma in a rat

Pleuropulmonary blastoma in an equine fetus

Pleuropulmonary blastoma (PPB) is a rare biphasic tumor of children formed by mixed epithelial-and-mesenchymal elements. In this article, the authors report a pulmonary mass in an equine fetus with characteristics of PPB. A soft multicystic broad-based pleural mass was identified in the right caudal lung lobe. The mass comprised solid areas of loose mesenchyme, fenestrated by small ducts or large cystic areas lined by cuboidal epithelium. Mesenchymal elements had moderate anisocytosis, anisokaryosis, and cellular pleomorphism and were immunoreactive for vimentin. Epithelial cells lining ducts and cystic lumina were nonciliated and cuboidal with central round nuclei, minimal cellular pleomorphism, and strong immunoreactivity for cytokeratin. Pertinent characteristics in common with human PPB were the pleural-based location, the dual solid or delicate multiloculated cystic structure, the primitive mesenchymatous stroma fenestrated by well-differentiated cuboidal epithelial-lined lumina, and the occurrence during gestation.

Bovine pulmonary blastomas: histomorphologic description and immunohistochemistry

Three adult female dairy cattle with pulmonary blastomas were evaluated. The gross lesions at postmortem were described as multiple white circumscribed masses throughout the lungs, with pleural involvement in one cow and lymph node metastasis in the other two cows. Histologically, the tumors contained a dual population of mesenchymal and epithelial neoplastic cells. Epithelial cells formed nests, tubules, and formations resembling bronchioles of normal lung. Mesenchymal cells were spindle shaped with oval nuclei and fibrillar eosinophilic cytoplasm, were large rounded cells with multiple round nuclei and granular eosinophilic cytoplasm, or appeared blast-like, with large hyperchromatic nuclei and amphophilic cytoplasm. The tumors varied greatly in appearance from one field to another within the same tumor. Epithelial cells stained positively with anticytokeratin antibodies. Some spindle-shaped mesenchymal cells exhibited smooth muscle cell differentiation with positive staining with anti-vimentin, anti-muscle-specific actin, and anti-smooth muscle actin antibodies, whereas other rounded mesenchymal cells expressed striated muscle cell differentiation with multiple nuclei and positivity to anti-neuron-specific enolase and anti-muscle-specific actin antibodies. The variable expression of the intermediate filaments and cytoplasmic enzymes indicates multiple pathways of differentiation in the pulmonary blastomas.