Rats are prone to a variety of lumps and bumps beneath their skin.  Many times these lumps and bumps are abscesses or infections that accumulate pus beneath the skin.  Sometimes the masses are enlarged lymph nodes.  In older rats, typically 18 months or older, tumors are more common as the cause of lumps and bumps.  The tumors may be benign ones such as adenomas or lipomas, or they may be more serious ones classified as adenocarcinomas.  Most tumors are readily removed at a small size and many of them do not return if the surgery was able to completely remove the growth.  If you see a bump on your rat, don't wait until it gets big to get it checked.  The sooner we see your pet, the better the chances are that we can help!

Mammary tumors are very common in unspayed female rats over 18 months old and in rats that were more than 4 to 6 months old at the time of spay.  About 10% of male rats develop mammary tumors.  Depending on the genetic strain of rat, around 90% of mammary tumors are benign which means they do not spread. Tumor removal does not guarantee that another tumor will not develop, but tumor removal in combination with a spay tends to significantly reduce the risk of new tumor formation or regrowth of the original tumor.  A rat that has a benign tumor and tumor removal and spay will typically live a full life.  Many younger rats have lived up to an additional 2 years following surgery.

Surgery is not the right choice for some rats.  Many rats do well without surgery and have a normal quality of life until the tumor is so large it interferes with movement or it develops scabs or ulcers.

If you decide to get a female rat as a pet in the future, it is very important to have it spayed when it is around 3 to 4 months of age. This eliminates the chance of ovarian disease and greatly reduces the chance of other reproductive diseases.  This also greatly reduces the chance of a rat developing a mammary tumor as she ages. It is one of the most important things you can do to extend her life.

Abscesses may be simple to treat after they have been surgically drained.  A course of antibiotics and anti-inflammatory medication may be all that is needed.  Some abscesses are resistant to treatment and may require multiple surgeries and more intensive medical therapy.  Abscesses on the face may be related to infected teeth and often require dental surgery.

Cysts are accumulations of material in the glands of the skin. Some cysts will rupture and ooze gray to yellow material.  Other cysts will need to be surgically removed.