Pleural effusion secondary to metastasis of an ovarian adenocarcinoma in a horse.

The research describes a case of an 11-year-old horse that developed a pleural effusion as a result of metastasized ovarian adenocarcinoma.

Case Presentation

• The horse was first observed with ventral edema and pleural effusion, which are signs of fluid accumulation in the tissue and lung cavity respectively. These were seen as secondary symptoms resulting from the spread (metastasis) of an ovarian adenocarcinoma.

Diagnostic Procedures

• In order to diagnose the cause, the researchers performed a bilateral thoracocentesis, another name for a pleural tap. This procedure extracts fluid from the pleural cavity for further examination.
• The extracted fluid was thin and tinged with blood, which characterized it as a modified transudate — an extracellular fluid that often contains higher levels of protein, cells, or solid materials.
• Further cytologic examination of this fluid revealed the presence of large atypical cells, generally indicative of a neoplasia, or abnormal tissue growth commonly associated with cancer.
• These types of cells were also found in the peritoneal fluid, which is another name for the liquid in the abdomen.

Pathological Findings

• The horse was euthanized and a post-mortem examination, or necropsy, was performed. The examination revealed a mass 35 cm in diameter in the cranial mediastinum, referring to a compartment in the chest beneath the trachea.
• The left ovary was found to have enlarged to 25 cm in diameter, with most of its normal tissue replaced by red or brown friable tissue with many small cysts. This was particularly suggestive of cancer.
• Based on the appearance and arrangement of tumor cells in the ovary, lymph nodes, and mediastinal mass, the cause of death was diagnosed as a papillary adenocarcinoma of the ovary – a form of cancer that originates in the ducts or glands and typically has a distinctive cellular growth pattern.

Conclusion

• The researchers concluded that when diagnosing causes for pleural effusion in horses, ovarian neoplasia should be considered as a possible cause.