Endometrial carcinoma in a young dog.

A 2-years-old nulliparous cross-bred bitch had persistent vulval discharge following treatments that included a combined ethinyloestradiol/methyltestosterone preparation and megoestrol acetate. The uterus, removed at ovarohysterectomy, contained a large polypoid intraluminal mass with the histological features of endometrial carcinoma. The bitch has remained well for thirty-one months after surgery. The possibility is considered that the lesion is drug-related but no firm conclusion can be drawn about the precise nature and pathogenesis of this unusual lesion.