Granulosa Cell Tumour in a Spayed Cat With Ovarian Remnant Syndrome and Hyperestrogenaemia Without Estrus Signs

BACKGROUND: Granulosa cell tumour (GCT) is the most common primary ovarian neoplasm in cats and may arise from residual ovarian tissue following incomplete spay procedures. OBJECTIVES: To describe the surgical management of a GCT identified in the setting of Ovarian Remnant Syndrome (ORS) in a spayed cat with hyperestrogenaemia without estrus signs, and to assess the potential utility of serum estradiol as an adjunct for diagnosis and postoperative monitoring. METHODS: A 6-year-old female domestic shorthair cat, reportedly spayed, presented with a 2-week history of weight gain and abdominal distension. Diagnostic imaging and cytology suggested a large neuroendocrine tumour occupying the abdominal cavity. Exploratory laparotomy was performed, and the abdominal mass along with one hepatic nodule was resected. RESULTS: Histopathology confirmed GCT in the abdominal mass with hepatic metastasis. A preoperative serum sample collected at initial presentation and assayed after receipt of the histopathology report showed markedly increased estradiol. Although clinical signs improved after surgery, the cat re-presented 4 weeks later with abdominal distension and severe anaemia; imaging revealed progression of hepatic lesions, and the patient died 5 weeks after surgery. CONCLUSIONS: This case highlights that GCT can occur in the setting of ORS without estrus signs, despite marked hyperestrogenaemia. Ovarian remnants may undergo neoplastic transformation and cause life-threatening disease, even in the absence of estrus signs. Serum estradiol may be a valuable marker for diagnosis, treatment response, and recurrence monitoring in feline GCT.