Proliferative Endometrial Lesions Hidden behind the Feline Pyometra

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 mul‐ tifactorial, but hormonal influences are suggested to play an important role in the patho‐ genesis. 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 endome‐ trium becomes atrophic. The severity of endometritis is variable. Thereby, the type of in‐ flammatory 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 expect‐ ed 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-exis‐ tence of feline endometrial adenocarcinoma (FEA). FEA 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 FEA, as well as molecular markers, have been recently described. Moreover, age is not an ade‐ quate factor for triage, since some FEA cases were described in young animals, prompt‐ ing 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 FEA that can worsen the prognosis.