Due to the small size of the mouse, evaluating its clinical phenotype is sometimes problematic. In contrast, mouse models are readily accessible to post-mortem analyses at any time during the course of a disease and prior to its clinical onset. RNA, protein, and histological analyses following sacrifice represent a powerful means to identify affected cell types and molecular events underlying the altered phenotype, and therefore to understanding the signaling or metabolic pathways involved. In this unit, an overview of post-mortem analyses is provided with a strong emphasis on the principles of routine histology, including tissue fixation, processing, embedding, and staining with hematoxylin and eosin. There are also several protocols for staining with specialized histological stains used in the metabolic field to detect intracellular lipids, intracellular lipid "ghosts", cholesterol esters, polysaccharides, mitochondria, pathological collagen deposits, and atherosclerotic plaques.

In this unit, a procedure for post-mortem examination of mice and tissue collection is provided. This procedure is performed for post-mortem analysis of anatomical defects (necropsy) and histological analysis and/or tissue collection destined for molecular biology applications. In both cases, tissue preservation is the major issue, but the way to achieve it depends on the objective. When histological analysis is the aim, tissue preservation is achieved by rapid transfer into fixative solutions. In contrast, molecular biology applications require rapid freezing of tissue samples to preserve mRNA integrity. Consequently, performing both procedures simultaneously may be at the expense of the final product quality.

Ectopic ovarian tissue is a rare gynecologic condition. Accessory ovaries were defined as excess ovarian tissue adjacent and connected to a normal ovary, while supernumerary ovaries were described as those ovaries situated away from normal ones. The one presented here is a case of a 20 year-old unmarried woman operated for recurrent abdominal pain. During laparoscopy we found a mass 2×1.5 cm in size in the ileum, located 80 cm from the ileocecal valve: the lesion was resected and an ileoileal anastomosis was performed, the anatomopathological examination of the mass proved to be ovarian tissue. The history of previous pelvic surgery with adhesiolysis, and the unusual location of the ectopic ovary, support the theory of an ovarian implant in the intestine, but the true ectopic ovary hypothesis is still probable because of the location of the ectopic ovary inside the intestinal wall. In any case, the location of ectopic ovary discussed here is unusual and perhaps unpublished before.