Practical pathology of aging mice

Pettan-Brewer, Christina; Treuting, Piper M.

Frequently, internal lesions not detected at physical exam, will be observable at necropsy. For example, in a mouse with labored respiration, the lungs may contain pulmonary tumors with an enlarged heart (Fig. 4G, H) . A mouse reported with head tilt or circling may be submitted to necropsy to rule out central nervous system disease, but is more likely to have otitis media/interna or arteritis impacting the vestibular system (31) . Neurological signs may be due to compression of brain tissue by intracranial neoplasias such as pituitary adenoma/adenocarcinoma (Fig. 5C,D) . Splenomegaly is a frequent non-specific necropsy finding that can be due to extensive extramedullary hematopoiesis, which occurs as a physiological response to stimuli such as chronic inflammation or neoplastic diseases (31) . With either cause, the spleen can be markedly enlarged (41) . Histology can aid in definitive diagnosis of gross lesions that have multiple differential diagnoses.