Some more info about previous question

Question
Hi,
I messaged about my female, ince, with the tumor.  just wanted to let you know that i took her to the vet as soon as i saw the lump, the vet said there was not much point operating because of her age.
Thanks,
Laura

Answer
Hi Laura

Thanks for telling me that. I probably would have asked about a vet in the message I sent you just a few minutes ago.

This is just one reason why I do not own female rats anymore. I only have males now until I am ready to have girls again and am ready to have them spayed at a young age to prevent these nasty tumors that I have come to despise so much. I have lost many females to these mammary tumors. Its heartbreaking.  I didn't tell you in the other message but will tell you about them and why our girls have them so much:

Mammary tumors form from high estrogen levels. They usually start to occur between 18 months and 2 years old     when the rat no longer goes in heat and her estrus cycles cease. At this time, the estrogen levels fuel both mammary tumors to develop and also pituitary tumors as well.

They can be removed, and its best to do it when they are small and have not become vascular making the surgery less of a risk since there are no major arteries involved yet.
The tumors remain subcutaneous and do not invade internal organs and area almost always benign. However, they become vascular and start to rob the rat of nutrients and this sustains the tumors life but depletes the rat of the proper nutrition she needs to remain healthy. In turn, her organs start to fail. So the tumor doesn't physically invade the organs by taking over in that sense, but the tumor still takes over the body when it becomes vascular.
This is when the rat starts to lose weight and cannot keep the organs healthy such as the liver, kidney and heart.
Often the tumor develops an abscess that leaks internally causing sepsis and this is often the cause of death from the tumor as well as organ failure.  
Spaying females at an early age (3 to 4 months) prevents these tumors from forming by up to 80 percent, but spaying is invasive which is what stops me from doing it.  Until I get brave enough to have any baby girls spayed (even though I trust my vet totally) I wont have any girls because I have lost too many from these tumors over the years and its heartbreaking.

Your a good rat mom and by taking her to the vet and trying to do the right thing for her shows how much she means to you.

Hang in there!