Mammary Tumours

The prevalence of mammary tumours in dogs is about three times greater than in women.

About 50% of all tumours in the bitch are mammary tumors. 

About 45% of mammary tumours are malignant (meaning they can spread to other parts of the body) in dogs. Spread of mammary carcinomas in dogs is primarily to regional lymph nodes and lungs, although they can spread to the bones also.
 

Mammary tumours in dogs are more frequent in intact bitches (bitches that have not been speyed). They are extremely rare in male dogs.

Ovariectomy (speying) before the first oestrus reduces the risk of mammary tumours to 0.5% of the risk in intact bitches.

Ovariectomy after the first oestrus reduces the risk to 8% of that in intact bitches. Bitches neutered after maturity have generally been considered to have the same risk as intact bitches
 
Mammary tumours are treated surgically.
 

The prognosis is based on multiple factors. Most mammary tumours that are going to cause death do so within 1 year.

Sarcomas are associated with shorter survival times than carcinomas. Other factors, including size of tumor, lymph node involvement, and nuclear differentiation, also affect the prognosis