Mast cell tumours in CD-1 mice

Area of Science:

• Veterinary Pathology
• Oncology
• Rodent Models

Background:

• Mast cell tumors (MCTs) are common in dogs but their spontaneous occurrence in laboratory rodents like CD-1 mice is less documented.
• CD-1 mice are frequently used in carcinogenicity studies, making their tumor incidence data valuable for risk assessment.

Purpose of the Study:

• To document the occurrence and characteristics of mast cell tumors in CD-1 mice used in long-term carcinogenicity studies.
• To analyze the distribution and potential associations of mast cell tumors with other neoplastic conditions.

Main Methods:

• Retrospective analysis of necropsy and histopathology records from CD-1 mice involved in carcinogenicity studies.
• Data collection spanned six years (1984-1989) and included 24,352 mice.
• Detailed recording of tumor location, multiplicity, and co-existing pathologies.

Main Results:

• Nine cases of mast cell tumors were identified among 24,352 mice (0.037% incidence).
• Eight of the nine tumors were multicentric, with widespread dissemination to organs such as bone marrow, lungs, liver, lymph nodes, and spleen.
• Associated conditions included intestinal adenocarcinoma, harderian gland adenoma, pulmonary adenocarcinoma, pleomorphic lymphoma, and cutaneous fibrosarcoma.

Conclusions:

• Spontaneous mast cell tumors are rare in CD-1 mice but can exhibit aggressive, multicentric behavior.
• The occurrence of MCTs in conjunction with other tumors highlights the importance of thorough histopathological examination in rodent studies.
• These findings contribute to the understanding of spontaneous tumor formation in mice used for toxicological and carcinogenicity testing.