Teratoma is composed of abnormal tissue derived from at least two and often all three germinal layers. They presumably arise from pluripotent germ cells that have undergone differentiation¹. Germ cells initially are found in the yolk sac and early in differentiation, migrate to the gonadal ridge. In the developing ovary, association of germ cells and sex cords precedes formation of primary follicles. Dysgerminomas and teratomas are tumors of domestic animals derived from germ cells². Teratoma cause spherical or ovoid enlargement of the affected ovary with solid and cystic areas on cut surface. It may contain sebaceous material and hair. A variety of other tissues may be present, including bone, cartilage, and teeth². Apart from ovary, teratoma was reported in retroperitoneal region³, adrenal teratoma in ferret⁴, lumbosacral region⁵ and cervical region⁶. Teratomas have been more frequently described in horses and are considered extremely rare in other animals⁷. Recently in domestic animals, cases of teratoma have been described in cats⁸, crossbred cattle⁹, water buffalo¹⁰ and dogs^11-13. Two percent cases of teratoma among the canine ovarian tumours were reported¹⁴. The present paper reported the rare incidence of ovarian teratoma in a 15- year-old labrador bitch.

A 15-year-old female labrador dog with history of anorexia and abdominal swelling was admited to Veterinary Clinical Campus, Veterinary College and Research Institute, Orathanadu, Thanjavur, Tamil Nadu. On radiographic examination a hypoechoic mass noticed in the abdominal cavity (Fig. 1). Surgical exploration revealed a large tumour mass in the let ovary and the whole ovarian mass was removed and sent for histopathological examination. The required tissue samples were collected and fixed in 10% formalin. The tissues were routinely processed, sectioned and stained with hematoxylin and eosin (H&E) stain.

Grossly, the ovarian mass was encapsulated with 2.5 kg weight and showed red, firm and irregular nodular appearance on the surface with engorgement of blood vessels (Fig. 2). On cut section of formalin fixed mass showed the presence of few cystic spaces, white hair fibers and more solid tissues (Fig. 3).

Histopathologically, ovarian mass revealed the presence of skin keratocyst, hair follicle and sebaceous gland (Fig. 4) of ectodermal origin. Presence of skin keratocyst with cartilage (Fig. 5) and cartilage cells (Fig. 6), osseous foci with adipose tissue (Fig. 7) of mesodermal origin. Presence of choroid plexus (Fig. 8), nerve (Fig. 9), neuropil tissue with neuron and glial cells (Fig. 10) of brain from ectodermal and mesodermal origin and also the presence of ovarian follicle.

The present case of ovarian teratoma was reported in 15 years old bitch but recent^11-13 as well as older literature³ reported in younger ages of 2 to 3 years old bitch. Presence of ectodermal tissues like skin keratocyst, hair follicle and sebaceous gland were in accordance with earlier reports^11,13. Presence of mesodermal origin of tissues like cartilage, bone and adipose tissue was similar with recent reports^12,13. Presence of choroid plexus, nerve and brain tissue was in accordance with recent finding¹², who reported the presence of the same along with retinal epithelium, ganglion cells and respiratory epithelium. Hence, the present case documented the rare incidence of ovarian teratoma in a labrador bitch.

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