A 3-year-old female dog was referred to the clinics of İstanbul University with the complaint of abdominal
distention. On the basis of the clinical fi ndings and ultrasonography, a mass was detected in the left ovary. An
ovariohysterectomy was performed. Grossly, the mass, with dimensions of 15 ~ 11 ~ 8 cm, weighed 1.2 kg and contained
hairs, cysts, fat, bone, and cartilage on the cut surface. Histology revealed the occurrence of well-diff erentiated
components of all 3 germ layers and the mass was diagnosed as a benign mature cystic teratoma.