Mast Cell Tumor | National Institute of Environmental Health Sciences Skip Navigation Mast Cell Tumor Close the left navigation Add The Digitized Atlas of Mouse Liver Lesions Much of the work carried out by DTT is in support of the National Toxicology Program (NTP), an interagency partnership of the Food and Drug Administration, National Institute for Occupational Safety and Health, and NIEHS. Visit the NTP Website Mast cell tumor in the spleen and liver of a mouse. Back to Top Last Reviewed: February 04, 2026