Equine Granulosa Cell Tumor

An equine granulosa cell tumor is a type of ovarian tumor common in mares (female horses). It develops from the granulosa cells, which are involved in hormone production. These tumors often cause hormonal imbalances, leading to behaviors like increased stallion-like tendencies or uneven fertility. Visually, affected mares may have a swollen or enlarged ovary, sometimes with a fluid-filled cavity. While these tumors are usually benign, they can impact a mare’s reproductive health and behavior. Diagnosis involves ultrasound and examination, and treatment often includes surgical removal of the tumor or ovary.