Leiomyosarcoma of the ovary in a young female guinea pig – a case report

This case report presents a one-year old pet female smooth-coated guinea pig with a diagnosis of leiomyosarcoma of the left ovary with locally aggressive behaviour. The animal had been showing lethargy and alopetic dermatosis for a few weeks. The mass in the area of the left ovary was suspected based on palpation, x-ray, ultrasonography of the abdominal cavity and the presence of the mass in the abdomen was confirmed by probatory laparotomy. Since the lesion was inoperable due to its size and infiltrative growth, the animal was euthanized. Leiomyosarcoma of the ovary with infiltrative growth into spleen and pancreas was diagnosed based on histopathological examination and the diagnosis was proved by immunohistochemical staining for the presence of smooth muscle actin. This is the first described case of this type of tumour in young intact female guinea pig. The case report could contribute to better understanding and knowledge of the occurrence of neoplastic changes of the ovary in guinea pigs especially for better treatment management and prevention of reproductive tract diseases. Ovarian tumour, ovarian cyst, reproductive problem, leiomyosarcoma Sommerey et al. (2004) proved that spontaneous tumours in general are relatively rare in guinea pigs (15% of 689 animals tested) with higher prevalence in older animals (39% of animals were > four years old). Leiomyosarcoma is a malignant neoplasm with uncertain pathogenesis. Rivas et al. (2014) suggested an origin of ovarian leiomyosarcoma from the smooth muscle of the blood vessels of the cortical stroma, as well as from the muscles around the corpus luteum and ovarian follicles, muscle fibres attached to the ovarian ligament, the remainder of Wolff’s duct, totipotent stem cells of the ovary, teratoma cells that have differentiated, or in smooth muscle cells that migrate from the uterus. The primary leiomyosarcoma was noticed e.g. in the heart of a three-year-old female guinea pig (Vogler et al. 2012), however, to our knowledge there is no report of ovarian leiomyosarcoma in this animal species. In women, the most common manifestation of leiomyomas is uterine and these neoplasms are called fibroids; ovarian leiomyosarcomas belong to highly aggressive tumours with hormonal influence (Fletcher et al. 2002; Divya and Srinivasamurthy 2014). In guinea pigs, cystic ovarian diseases, such as cystic rete ovarii, are also affected by hormones and are more often observed in aged females (Paterson 2006). Serous cysts are normal components of cyclic ovary in guinea pig (Shi et al. 2002). The aetiology of ovarian cysts is unknown, but a certain role may be played by oestrogenic substances in hay. Cysts are usually asymptomatic, however, as they increase in size (can be up to 10 cm in size and fill in a large part of the abdominal cavity), non-pruritic alopecia, abdominal enlargement and infertility may be observed. Cystic ovaries are often associated with concurrent diseases in the reproductive tract (Keller et al. 1987; Paterson 2006). Diagnosis of ovarian cysts is based on history, abdominal palpation, radiography, and ultrasonography. ACTA VET. BRNO 2017, 86: 269-272; https://doi.org/10.2754/avb201786030269 Address for correspondence: MVDr. Radka Lukášová Department of Biology and Wildlife Diseases Faculty of Veterinary Hygiene and Ecology University of Veterinary and Pharmaceutical Sciences Palackého tř. 1946/1, 612 42 Brno, Czech Republic Phone +420 603 808 002 radka.lukasova@email.cz http://actavet.vfu. cz/ The aim of this study was to report a rare case of ovarian leiomyosarcoma in the guinea pig.