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Pet Rats/Female rat possible tumor


Hello Irene,
You were very helpful to me and my lovely rat Dee about 2 months ago, and I wondered if you were able to advise me again? Dee is about 20 months old and female. Two months ago she had a large lump removed from her lower abdomen, it appeared very quickly and grew very quickly, but the surgery was successful and she has healed very well, and was surprisingly well behaved throughout her whole ordeal. I didn't know about this problem with female rats and was so worried about her, you advise me to get the lump removed and we are very grateful, as it was definitely the right decision.
A week ago I noticed (as I now check both my girls regularly) she has a tiny lump under her armpit. I wasn't shocked as knew this might happen. It hasn't grown yet though and I have heard it could just be a cyst so do you think it would be best to leave it for the time being, or is it better to have it removed when small (it's no bigger than a pea at the moment).
As I used my savings for the last recent op is there anything I can do/ feed her to try and keep it small, to give me time to save the money rather than try and borrow it?
I also wondered if she does need a second operation, should I get her spayed at the same time? I'm not sure of the risks of this, would it mean she wouldn't get any more tumors in the future?
The vet I used was very nice and seemed well informed, he told me they couldn't be sure what the lump was until they removed it. Would you agree with this? If it is just a cyst would it get bigger and how long would it last?
Sorry I have a lot of questions, if she needs surgery I will find the money to do it, but don't want to have to go through the whole thing again if its unnecessary. But at the same time I don't want to leave it if it would be better operated on while small. Do they all grow at different rates? How many can I expect she will have in the future?

Thank you for your help and Merry Christmas.


I'm sorry for not getting back to you sooner but the holidays had me so busy.  Yes, I do remember helping you with Dee a little while back.  I am so glad everything turned out well with the surgery.

First just a little information:  cysts can form in the hair follicle or in the skin's pores.  In many cases, a rat may scratch the cyst and break the skin, which can lead to a pocket of infection below the skin creating an abscess.

I definately do not agree with what your vet said.  He should be able to tell the difference between a cyst and a tumor by the way it feels.  The other main difference between the two types of lumps that would be a sign for you to tell is the speed of the lump's growth.  A cysts or abscess tends to grow very large very quickly.  It can go from a pea size to a large grape size in a day or two.  Tumors, on the other hand, typically grow much slower.  Tumors tend to all grow at generally the same rate.  To grow from a pea size to a golf ball size takes about 3 months.

Tumors tend to be hard beneath the rat's skin.  Cysts and abcesses are generally firm but softer since they're filled with sebum, pus or fluid.  Cysts are located at the level of the skin, while tumors tend to be situated below the skin's surface.  One easy way to tell if the lump is at skin level is by placing a finger on either side of the lump and pulling the skin between your fingers taught, and moving your hand back and forth.  If the lump is at the skin level, it will move with the skin. If the lump is below skin level, it will appear stationary as the skin moves over the lump.

A cysts or abscess should NEVER be surgically removed, so be careful with the vet and make sure they don't try to do that.  A cyst or abscess will sometimes begin draining naturally, so discharge is not uncommon, but if you (or your vet) can determine for certain it's a cyst or abscess, I recommend you have the vet lance and drain it (often this takes multiple times before healing is complete) and oral antibiotics are often prescribed.

There is no need to rush into surgery so quickly.  You should be able to tell by the rate of the growth whether it is a tumor or cyst, so I suggest you wait at least a week.  Yes, it's true tumors are safer to surgically remove when they are smaller, but even a tumor the size of a large grape is relatively small.  When I had a tumor removed from my female rat recently, it was the size of a golf ball, and everything was fine.

I don't know the qualifications of your current vet, but because he told you he couldn't tell the difference between a cyst and tumor, I'd be apprehensive.  I recommend a second opinion from a vet who is either an exotic vet or who has experience with rats.  

If this does turn out to be a tumor and you have it surgically removed, don't bother to have Dee spayed at the same wouldn't help at this point.  Spaying has to be done while a female rat is very young in order to prevent tumors.  Once female hormones start being released, it is too late.  You can probably expect future tumors, but I can't say for certain because every rat is different.  If she does get more tumors, you can continue to have them removed, but there will come a point in her life, when she is old and more frail, or if your vet determines in a pre-op exam that she is too old or unhealthy for the surgery to be safe, that you must allow the tumor to take it's course and have her humanely euthanized when her quality of life begins to suffer.  You are not at this point yet, and hopefully Dee will live to a healthy ripe old rattie age, so let's just take this one step at a time.  I will be more than happy to help you every step of the way, so once it's determined cyst or tumor, write back to me and we can take it from there if you like.

Good luck and I hope for the best for your precious girl.

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Irene Murphy


I can answer a variety of questions regarding adoption and care of pet rats throughout their lifetimes, including questions about their health and well being, temperment, diet, bedding, cages, toys, etc. I will try to answer your questions to the best of my ability in a timely manner and I have an abundant amount of resources to help me to help you with your pet rats. I love rattie pictures, so include pics with your question if you can. You may ask me medical questions, but please be advised that I am not a vet. I may use my resources to answer some medical questions, however, I will need to refer you to your local vet with medical questions that I feel I am not qualified to address.


I have been a huge rat enthusiast for many years. Since becoming a rat owner, I have educated myself in all areas of pet rats from every resource I could find including the internet, books, conversations with local exotic vets, as well as several local rat breeders.

I have a college degree but not in the area of animals. I have obtained my extensive experience and knowlege of pet rats all on my own because in my eyes, pet rats are the most interesting and fascinating creatures you can ever imagine to have as pets. I also am saddened by how mislabeled and misunderstood these amazing and extremely smart animals are by the majority, and my mission in life has become to educate and change as many people's perceptions of rats as I possibly can.

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