The following guidelines apply to tumors generated in rodents.

  • Tumor burden is not judged on a generic size criterion, since the impact of a tumor will vary depending on its location. Rather, the impact of the tumor(s) on the health and well-being of the animal is key. Animals must be euthanized before or when tumor burden either (1) interferes with the animal’s ability to ambulate or to reach food or water; (2) obstructs or impinges on the opening of any orifice (e.g., eye, ear, nose, mouth, respiratory tract, urinary tract, or rectum); or (3) reaches a level that otherwise interferes with normal activity or body functions, or causes apparent distress or discomfort to the animal.
  • Exceptions to the above may be allowed only after ARC approval of a detailed scientific justification and description of the procedures to be undertaken to protect the health and welfare of the animal. Such procedures should be developed and updated as needed in collaboration with a member of the DLAM veterinary staff.

Tumors in body cavities, such as the cranium, orbit, abdomen, or chest, or in other restricted locations, such as bone marrow cavities or in the testes, may severely impair physiological or neurological function. Therefore, animals with these types of tumors must be euthanized when such signs become apparent, regardless of tumor size, unless otherwise justified in the ARC approved protocol. In such cases, investigators are expected to follow the monitoring and premature euthanasia criteria as described in their protocol.

Body weight is not always an accurate indicator of animal health when a tumor is present. In animals with tumors, evaluation of body condition score (BCS) is recommended. No animal should be allowed to reach a BCS of less than 2 out of 5 unless it is scientifically justified and approved by the ARC. For more information on body condition scoring, please refer to "Determining Rodent Body Condition Score."

The following specific guidelines must be followed, unless ARC approval for a departure is obtained:

  • Animals must be euthanized before or when the tumor becomes ulcerated. Ulcerations represent nonviable tissue that will not heal, and they cannot be surgically repaired. An ulcerated tumor may appear as an open, moist lesion or as a scab, which is indicative of a break in the underlying epithelium. Any disruption of the skin, even pinpoint, represents ulceration. If a rodent is receiving experimental treatment that may be expected to result in ulceration or necrosis, please account for this in your animal use protocol.
  • Any animal that is moribund, cachectic, or exhibits any of the criteria for premature termination specified in the approved protocol must be euthanized.
  • Investigators must clearly label all cages that contain rodents into which foreign cells have been injected with (1) the date and site of injection/implantation, (2) the cell line identity, and (3) the name and phone number of the individual primarily responsible for monitoring the animals. DLAM has tumor cards available for use, though the ARC does not require use of these cards.
  • It is the responsibility of the principal investigator (PI) to ensure that animals are observed daily, including weekends and holidays, to monitor tumor development and to evaluate overall clinical condition. Such monitoring must take into account loss of body condition and indications of pain, distress, or abnormal behavior and physiology, as detailed in the Guide for the Care and Use of Laboratory Animals and the approved protocol.
  • Changes in the animal’s clinical condition or in the integrity of the skin overlying the mass can occur rapidly. Through daily observation, these changes should be noted by the PI/ PI’s staff. If a cage is posted by DLAM animal care staff, the lab must ensure that the animal is evaluated and euthanized if the criteria above are met. Alternatively, the case may be discussed with a DLAM veterinarian and an endpoint determined.
  • For guidelines on growth of ascitic tumors, please refer to the ARC Policy on Monoclonal Antibody Production.

Exceptions to this policy may be permitted on a case-by-case basis after consultation with a DLAM veterinarian, provided that the health and well-being of the animal is not impacted. Routine exceptions to this policy must be reviewed and approved by the ARC prior to initiation.

Approved 11/13/00; Revised 2/11/02, 3/11/02, 7/26/04, 9/12/05, 4/24/06, 10/23/06, 9/23/13, 1/12/15