New Tumor Burden Policy for Rodents Announced

May 29, 2019

Information icon for new rodent tumor policyThe Institutional Animal Care & Use Committee (IACUC) recently approved a new Tumor Burden Policy for Rodents. This new policy was requested by, and includes substantial input from, the Animal Care & Use Faculty Advocacy Committee (ACU-FAC), and aims to:

  • Reduce the laboratory burden associated with tumors,
  • Eliminate the need to maintain tumor monitoring records in the animal room, and
  • Provide standard tumor endpoints for mice and rats with externally visible tumors that allow for flexibility if scientifically needed.

Please note that standard tumor endpoints do NOT replace what is already described in an IACUC approved protocol. Research personnel will continue to have the same responsibility to ensure tumor-bearing animals are removed from the study when they reach the defined humane endpoint(s).

Additional Policy Details

Animals with conditions exceeding the following external tumor endpoints must be euthanized:

External tumor size

  • For mice, a tumor diameter measuring greater than 2 centimeters (cm) in any single dimension
  • For rats, a tumor diameter measuring greater than 4 cm in any single dimension

External tumor location

  • A tumor that impairs the normal movement/physiologic behaviors of the animal
  • A tumor in locations where tumor growth is limited by the anatomy of that area, such as the face


  • A tumor ulceration that is greater than ½ the surface area of that tumor
  • Any tumor ulceration that has effusions, appears infected, or has hemorrhage

Please review the full Tumor Burden Policy for Rodents for complete details, including important changes to animal room procedures.

With the understanding that this new policy will impact laboratories in a number of ways, we are offering the following resources:

Available Resources

The Animal Care & Use Office (ACUO) is available to submit protocol amendments on behalf of study teams to:

  1. Align protocol(s) endpoints with the new Policy endpoints, or
  2. Add scientific justification for exceeding the endpoints outlined in the new Policy.*

Option 2 requires a Request for Special Treatment or Procedure (SToP) Form, which the ACUO will provide.

If you have additional questions about how the new policy will affect your protocol, or if you would like to request assistance with submitting an amendment to your existing protocol(s), please contact your Research Compliance Associate in the ACUO.

To support investigative personnel in this recent policy change, an MLearning online training module is available. Use the following link to log in to MLearning, then launch the module: ULAM-12100 Rodent Tumor Study Monitoring and Management.

The module will appear in the individual Learning Plans of those who are listed as handling rodents on an IACUC animal use protocol with a tumor growth procedure.

This module is IACUC recommended, not required, and provides information to:

  • Learn the IACUC requirements for monitoring animals undergoing tumor studies
  • Identify health concerns and humane endpoints related to tumor growth and ulceration
  • Identify and monitor tumor development
  • Know how to obtain veterinary care

For additional assistance with tumor monitoring training, please contact the ULAM Training Core at or (734) 764-8039.

Members of the Unit for Laboratory Animal Medicine (ULAM) and the ACUO will be hosting two informational sessions to answer questions and provide guidance and resources for the new Tumor Burden Policy for Rodents.

Principal Investigators and laboratory staff are both invited to attend. No RSVP required.


2:00 PM - 3:00 PM
ROOM M3330


10:00 AM - 11:00 AM