Rat Tumors

White rat on black background
Getty Images/CONEYL JAY

Pet rats are far more lovable than many people think and anyone who has one knows this. Some of the best things about rats is that they develop such unique personalities and are incredibly smart. Unfortunately, rats tend to have short lifespans often cut even shorter due to tumors.

Kinds of Rat Tumors

Rats, like dogs and other kinds of pets, can get a variety of different kinds of tumors (also referred to as masses) in and on their bodies. Some tumors grow quickly and are very obvious while others are more hidden and go unnoticed until your rat starts acting differently. Your veterinarian will be able to determine what kind of tumor your rat has by feeling it and potentially obtaining a biopsy or cytology of it to determine whether or not surgery is needed.

  • Mammary Tumors - These tumors can be benign or malignant (cancerous or non-cancerous) and grow in the breast tissue of both male and female rats (yes, boys have breast tissue). Mammary tumors can be very fast growing and large, sometimes encompassing an entire side of a rat. If they start to seep fluid it usually has a creamy, milky consistency, or is very chunky with a tinge of blood. These masses can be surgically removed by your exotics vet but since it can be very hard to completely remove all of the affected breast tissue, regrowth is common. Spaying or neutering your pet rat may help reduce the likelihood of your rat getting breast tumors (which are usually a specific kind of cancer called fibroadenomas) but there are no guarantees since we do not completely understand the reasons behind why rats get them.
  • Lipomas - Also known as fatty tumors, these growths are exactly what their name implies - fat. Many species of animals get lipomas (and so do people!) and there isn't any way you can prevent these tumors from popping up on your pet rat. These are non-cancerous growths but can grow very large and make it difficult for your rat to move around. These tumors are usually removed to help regain movement when your rat is having a problem getting around due to their large size or location (such as in an armpit).
  • Cysts - Male rats are most prone to getting cysts. A cyst is a fluid-filled sac (similar to a very large zit) and not actually a tumor (unless it is a cystadenoma) and can be found on the inside or outside of your rat. Males will often get cysts on their back where their sebaceous glands are extra active but females can get ovarian cysts. Cysts can even pop up just from a bad skin infection. They are usually lanced or popped by your vet and the fluid, or thick secretion, is squeezed out. They can reoccur unless surgically removed but they don't usually cause a major issue unless they become infected. They are usually quite firm and do not typically get as large as a lipoma or mammary tumor.
  • Brain Tumors - These tumors cause neurologic symptoms and may or may not be able to be seen on your rat since the skull usually hides them. Brain tumors are inoperable in rats and they should be euthanized if their quality of life is compromised by one. Bulging eyes due to a tumor in the brain pushing on them or a misshapen head are the most commonly seen indicators of a brain tumor unless your rat was to get an MRI or CT scan.

    Other kinds of tumors also exist but aren't as commonly seen in rats as the aforementioned types. Specific kinds of tumors such as fibrosarcomas, fibromas, and squamous cell carcinomas can all be difficult to completely remove and grow very quickly on different parts of the body including the face. Some tumors may be very uncomfortable for your rat while others may not bother them at all.

    Not all vets treat exotic pets and not all exotic vets will operate on a rat. If your rat needs surgery be sure to find an experienced exotics vet that you feel comfortable working with. You may also want to ask for the tumor to be sent for a histopathology (biopsy) review to know exactly what kind it was.