BackgroundGranulosa cell tumors (GCTs) account for approximately 2% of ovarian malignancies and are considered a rare type of ovarian cancer. GCTs are characterized by irregular genital bleeding after menopause due to female hormone production as well as late recurrence around 5–10 years after initial treatment. In this study, we investigated two cases of GCTs to find a biomarker that can be used to evaluate the treatment and predict recurrence.Case presentationCase 1 was a 56-year-old woman who presented to our hospital with abdominal pain and distention. An abdominal tumor was found, and GCTs were diagnosed. Serum vascular endothelial growth factor (VEGF) levels decreased after surgery. Case 2 involved a 51-year-old woman with refractory GCTs. Carboplatin–paclitaxel combination therapy and bevacizumab were administered after the tumor resection. After chemotherapy, a decline in VEGF levels was observed, but serum VEGF levels increased again with disease progression.ConclusionsVEGF expression may be of clinical importance in GCTs as a clinical biomarker for disease progression, which may be used to determine the efficacy of bevacizumab against GCTs.