Pleuropulmonary blastoma in an equine fetus.

This research article explores a case of Pleuropulmonary blastoma (PPB) – a rare tumor generally affecting children – found in an equine fetus. The authors share their findings about the pulmonary mass and identify characteristics that are consistent with human PPB.

Discovery and Description of the Mass

In this study, the researchers discovered a pulmonary mass in an equine fetus that had similar characteristics of Pleuropulmonary blastoma. This is unusual, considering PPB is usually found in children and rarely reported in animals, let alone equine fetuses. The mass was found in the right caudal lung lobe. Upon examination, it appeared as a soft multicystic broad-based pleural mass.

• The mass consisted of the mixed epithelial-and-mesenchymal elements typical of PPB
• The solid areas of the mass were made up of loose mesenchyme, which is a type of embryonic connective tissue
• These areas were fenestrated, or had openings or gaps, through which were small ducts or large cystic areas. These were lined by cuboidal – or cube-shaped – epithelium

Study of Cellular Components

The study further dove into the cellular components of the mass:

• The mesenchymal elements showed moderate anisocytosis (a condition where cells are not of an equal size), anisokaryosis (nuclear atypicalities), and cellular pleomorphism (the occurrence of multiple forms)
• They were immunoreactive for vimentin, a protein commonly shared between different types of cells and associated with cell and tissue structure
• The epithelial cells that lined the ducts and cystic lumina were nonciliated and cuboidal in shape with central round nuclei
• They showed minimal cellular pleomorphism and had a strong immunoreactivity for cytokeratin, a type of protein that contributes to the integrity of epithelial cells

Comparison to Human PPB

The discovery of these characteristics in the equine fetus was notable because they closely reflect the same characteristics found in human cases of PPB. These include:

• The location of the tumor on the pleural, or lung tissue
• The structure of the tumor itself, which can either be solid or have a delicate multiloculated cystic structure
• The presence of a primitive mesenchymatous stroma, a supportive tissue, fenestrated by well-differentiated cuboidal epithelial-lined lumina
• The occurrence of the disease during gestation, or the period of development within the womb

Therefore, the findings could potentially add significant value to the comparison and study of PPB across different species.