It's known that canine mammary tumors are very similar to breast cancer in humans, but it wasn't clear how similar until researchers at the University of Zurich in Switzerland took a closer look.

Breast cancer is the most common cancer in women both in developed and undeveloped countries. It's estimated that over 508,000 women globally died from the disease in 2011, according to the World Health Organization.

The research team examined the surrounding tissue of canine mammary tumors using molecular biology and immunohistological methods. The tissue was from an archive at the Institute of Veterinary Pathology in Berlin.

"With the permission of our patient's owners, we conduct pathological tests to better understand diseases," Alexandra Malbon, one of the researchers and animal pathologist at the university, said in a statement. "In the process, we archive samples of various organs and tissues, as these samples can be of great value to answer future research questions."

The team was able to prove that some cells surrounding the tumors behave the same way as the corresponding cells in humans. In both cases, substances are produced in the healthy surrounding tissue that promote tumor growth.

They concluded that canine tumor tissue is much more suitable for human breast cancer research than tissue from rats or cells cultivated in the lab. It was also noted that they don't view the dogs as test subjects, but rather patients themselves.

"They can help us to better understand breast carcinoma in both dogs and humans and fight it more effectively," said Dr. Enni Markkanen, corresponding researcher and junior group leader at the Institute of Veterinary Pharmacology and Toxicology.

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