The mammary pathology of genetically engineered mice: the consensus reportand recommendations from the Annapolis meeting

NIH sponsored a meeting of medical and veterinary pathologists with mammary gland expertise in Annapolis in March 1999, Rapid development of mouse mam mary models has accentuated the need for definitions of the mammary lesions in genetically engineered mice (GEM) and to assess their usefulness as mod els of human breast disease. The panel of nine pathologists independently r eviewed material representing over 90% of the published systems, The GEM tu mors were found to have: (1) phenotypes similar to those of non-GEM; (2) si gnature phenotypes specific to the transgene; and (3) some morphological si milarities to the human disease. The current mouse mammary and human breast tumor classifications describe the majority of GEM lesions but unique morp hologic lesions are found in many GEM. Since little information is availabl e on the natural history of GEM lesions, a simple morphologic nomenclature is proposed that allows direct comparisons between models. Future progress requires rigorous application of guidelines covering pathologic examination of the mammary gland and the whole animal. Since the phenotype of the lesi ons is an essential component of their molecular pathology, funding agencie s should adopt policies ensuring careful morphological evaluation of any fu nded research involving animal models. A pathologist should be part of each research team.