Mammary tumor

It is a common finding in older female dogs and cats that are not spayed, but they are found in other animals as well.

The mammary glands in dogs and cats are associated with their nipples and extend from the underside of the chest to the groin on both sides of the midline.

[3] Multiple studies have documented that spaying female dogs when young greatly decreases their risk of developing mammary neoplasia when aged.

Overall, unspayed female dogs have a seven times greater risk of developing mammary neoplasia than do those that are spayed.

[6] Obesity at one year of age and eating red meat have also been associated with an increased risk for these tumors,[7] as has the feeding of high fat homemade diets.

[8] There are several hypotheses on the molecular mechanisms involved in the development of canine mammary tumors but a specific genetic mutation has not been identified.

[9] Inflammatory carcinomas describe tumors that are fast growing and have bruising, edema, and pain, and can also cause disseminated intravascular coagulation.

[10] Malignant tumors are also subdivided histopathologically into those showing blood vessel wall invasion and those that do not.

[5] Furthermore, current data show that significant similarities and differences exist between canine and human mammary tumors at the molecular level.

In addition, newer studies showed that certain gene expression patterns are associated with malignant behaviour of canine mammary tumors.

Because 40 to 50 percent of dog mammary tumors have estrogen receptors,[11] spaying is recommended by many veterinarians.

[12] However, several other studies found no improvement of disease outcome when spaying was performed after the tumor had developed.

[18] Siamese cats and Japanese breeds seem to have increased risk,[19] and obesity also appears to be a factor in tumor development.