The literature refers to pyometra as the most important pathology in the feline uterus, which is often associated with cystic endometrial disease cystic endometrial hyperplasia/ pyometra complex or CEH-Pyo . The etiology of pyometra is complex and probably multifactorial, but hormonal influences are suggested to play an important role in the pathogenesis. Progestagen-based contraceptives may be risk factors for the CEH-Pyo syndrome, for endometrial adenocarcinoma and also to mammary tumors in this species.The histopathological descriptions of pyometra include an enlarged uterus containing purulent fluid, variable endometrial infiltration of neutrophils and bacterial colonization. The degree of hyperplasia of endometrial glands is variable, and frequently the endometrium becomes atrophic. The severity of endometritis is variable. Thereby, the type of inflammatory cells infiltrating the uterine wall or lumen varies accordingly and may include neutrophils, macrophages, plasma cells and lymphocytes.The clinical diagnosis of pyometra is often based on the clinical signs and the physical examination, supported by ultrasound findings. The surgical excision of the uterus is the recommended treatment when the animal is not intent for breeding, as most pyometra clinical signs resolve after ovariohysterectomy.Nevertheless, our clinical practice demonstrated that, in cats, pyometra often masks other uterine conditions that may present a worst prognosis and may interfere with the expected outcome. Thus, although seldom requested, the pathological analysis of the uterus with pyometra should be performed following surgery, even if significant macroscopic alterations are not visible, as one frequent finding in pyometra specimens is the co-existence of feline endometrial adenocarcinoma FE" . FE" is usually described as a rare pathology in cats, but recent descriptions suggest that it may be more frequent than thought. Some morphological and clinical features of FE", as well as molecular markers, have been recently described. Moreover, age is not an adequate factor for triage, since some FE" cases were described in young animals, prompting pathologists, clinicians and researchers into this new reality.© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Therefore, this chapter proposes to highlight aspects that reinforce the need for careful observation of all the cases of CEH-Pyo, to exclude the co-existence of FE" that can worsen the prognosis.Keywords: Cat, cystic hyperplasia, endometrial adenocarcinoma, pyometra, queen
. IntroductionThe cystic endometrial hyperplasia-pyometra CEH-Pyo complex is the most frequent and important uterine disorder in queens [ ]. Ovarian hormones are considered the main factors in CEH-Pyo complex development, and progesterone is considered the principa...