Common Cancers and Tumors in Rats

2 min read


Rats are genetically predisposed to a high incidence of tumors and cancers. Some tumors may be malignant while others are benign. In all cases, however, it is advisable to remove the tumor to help reduce the fatalities as a result of the cancerous growths.


Symptoms and Types



  • Benign tumors of the skin that develop in the chest, back or tail.

Mammary Fibroadenomas

  • The most common kind of reproductive tumors in rats.
  • Can be found in the mammary (breast) tissue, and are usually benign (not malignant).
  • Found in both female and male rats.

Mammary Adenocarcinomas

  • Malignant (aggressive and spreading) tumors that are found under the skin anywhere on the underside of the body, from the chin to the tail, as rats have widely distributed mammary (breast) tissue.
  • Typically these tumors are soft, round, or somewhat flat growths that can be moved

Pituitary Gland Tumors

  • Common in female rats.
  • Due to the position of the tumor, symptoms include head tilting and depression.
  • These tumors usually lead to sudden death

Testicular Tumors

  • Found in the testes of male rats

Zymbal’s tumors

  • Found at the base of the ear in older rats; they are relatively infrequent




Rats by nature are very susceptible to the development of tumors. Some are more common than others, of course. For example, mammary adenocarcinomas are common in rats because of their widely distributed mammary tissue. Tumors of the pituitary gland increase in occurrence in relation to increased consumption of high-calorie foods.




Tumors growths that can be seen or felt externally are the easiest to diagnose. Tumors that occur in the internal organs can only be diagnosed wih the assistance of X-rays and other scans.