For more in-depth information on treating and scientific facts, please click here . Every female rat I have ever had has, at some point, grown a tumor. Usually spaying females decreases the chance in getting them. Male rats are less prone to get them. Tumors can be either benign or malignant.
Benign tumors are non-cancerous and can be removed in surgery.
Keep in mind, though, not all lumps are tumors. Some are abscesses . Abscesses, which are under the skin, are infections that are commonly caused by injuries due to another rat. An abscess usually requires treatment with antibiotics, and you should go to the vet. Also go to the vet if there are abscesses or pus around the jaw.