Feline endometrial adenocarcinomas

Endometrial adenocarcinomas are considered to be rare in domestic animals, in particular comparing to non-epithelial tumours of the uterus such as leiomyoma, in part because they are likely underdiagnosed. In cats, though uterus was the most common site for genital tract tumours, endometrial adenocarcinomas were found to be rare in all available references. In the study presented herein, forty feline primary endometrial adenocarcinomas, identified by a minimum of three pathologists on conventional haematoxylin and eosinstained sections, obtained from the archives of four different laboratories, for a period of 13 years were used in a retrospective study on the subject. In previous studies on feline endometrial adenocarcinomas (FEA) it has been found an increase incidence in purebred animals, which has been associated with a longer reproductive activity in those animals in comparison with domestic cats. However, this should be read with caution, as population ratios between purebred and domestic mongrel animals may change with the geographic location. Also the cultural adoption of gonadectomy as a contraceptive measure may interfere with the regional prevalence of the disease. In fact, in Portugal the number of intact domestic cats is higher than the purebreds, due to the tendency for late spaying age (most of them due to uterine or mammary diseases), which could influence the incidence of FEA in our country. Some of the specimens used in this study were obtained at ovariohysterectomy following a clinical diagnosis of pyometra. Unless metastasic disease exists, to which illness is often associated, most frequent signs for FEA are vague and unspecific, making difficult the early diagnosis of endometrial carcinoma. The histological evaluation shows the existence of different tumour phenotypes, where clear cell are often found. The presence of nuclear atypia and the Ki67 expression seem not to be related to the malignancy of the tumour. Furthermore, one report refers the presence of oestrogen receptors, which could explain the low levels of metastization or invasiveness proposed for FEA, or the clinical outcome for the tumour. For most situations of primary FEA, in particular in early stages of the disease, myometrial invasion is limited and often absent. Also vascular invasion is seldom observed even in tumours with moderate nuclear atypia. However, limited information exists on specimens from early FEA stages, which impair the presentation of a reliable prognosis for that animal. The major challenge seems to be the identification of valuable prognostic markers to achieve a definitive prognosis for animal life. Feline endometrial adenocarcinomas are possibly more common than we might presume and the clinical impact of such tumours may be increasing with the increase in the ability to establish an early diagnosis allied to an extended duration of life in cats. A recent report defends that FEA are more common than smooth muscle tumours of the uterus. Furthermore, as it frequently co-exists with pyometra or mucometra, it is also possible that a large number of cases fail to reach the pathological evaluation and hence remain undiagnosed. In this chapter we propose to discuss the clinical and morphological data of all the forty feline primary endometrial adenocarcinomas, supported by an extended review of the literature.