Abstract
Sex cord stromal tumours are the most common reported form of ovarian neoplasm in all animal species. The term lipid cell tumour has been used, and the term steroid cell tumour has been proposed for the ovarian neoplasm composed of large rounded or polyhedral cells that resemble luteal, interstitial, or adrenal cortical cells but cannot be identified as any one of those.
The present study describes a case of an ovarian tumour that resembles a lipid cell tumour in an eight years old Patagonian sea lion.
Serum biochemical analysis five days before death were within the normal range for the animal with blood urea nitrogen of 15 mg/dl and creatinine 0.9 mg/dl, and liver enzymes: alanine aminotransferase 24 IU/L, aspartate aminotransferase 28 IU/L, gamma glutamyltranspeptidase 161 IU/L, and alkaline phosphatase 88 IU/L. Complete blood count results were within the normal reference ranges: WBC 10200*106/L (7000-13800* 10^6 / L) and RBC 4.32 * 1012/ L (3,84-5,29 * 1012/ L).
The animal, with a previous history of chronic gastrointestinal problems, was anesthetised for a gastroscopy. Forty minutes into the procedure the animal did a cardiac arrest and was resuscitated. However, she never regained full consciousness and died some hours later.
Necropsy revealed, among a chronic gastro-intestinal enteritis and chronic pneumonia and focal thickening of pleura, a 3 x 4 x 3 cm tumour that replaced the right ovary. The neoplasm consisted in a solid mass of dense sheets and nests of round to polyhedral irregularly shaped cells with abundant finely vesiculated cytoplasm. The nuclei were uniformly small and round to oval.
The supporting stroma contained theca cells. The immunohistochemical staining profile showed positivity for inhibin, vimentin and focal positivity for cytokeratin.
In the California sea lion, Zalophus californianus (Lesson, 1828), a significant association between urogenital tumors and endemic Otarine Herpesvirus-1 (OtHV-1) infection has been described. Further investigations are necessary to evaluate the possible association of a viral infection with this unusual ovarian tumour as well.