A 9-year-old spayed female Flemish cattle dog was presented with a history of vaginal discharge and a slowlyprogressive bilateral symmetrical alopecia on the neck, shoulders and flanks, ventral abdomen and the perineal area.Clinical examination revealed pattern alopecia with the presence of macular melanosis on the ventral abdomen andin the perineal area. The dog also had a swollen vulva and gynecomasty. Abdominal ultrasonography revealed thepresence of two intact ovaria (with cystic follicles in the right ovarium) and a stump pyometra. Ovariectomy andstump removal were performed. Histopathological examination demonstrated that one polycystic ovary wascharacterized by multiple follicular cysts. The collection of all data led to the diagnosis of hyperestrogenism causedby a cystic ovary. This case demonstrates that even with a misleading history (spayed bitch) a correct interpretationof skin lesions can lead to the diagnosis of hyperstrogenism due to ovarian cysts.