I like to see couple more low power photos. What about mitosis? Any focal luteinized cells? Anyway, I toss some differentials for your consideration:

1. Cellular Fibroma, if active mitosis, consider Mitotically active cellular fibroma

2. Endometrial Sarcoma of the ovary (CD10, ER and PR)

3. Granulosa cell tumor (Inhibin, calretinin, retic stain)

4. Krukenburg tumor:  whenever you see a spindle cell neoplasm in ovary, you should always include spindle variant of Krukenburg tumor in your differential to make sure rule out metastatic carcinoma. (AE1/3 should be positive)