Are cancerous ovarian tumors fast or slow growing?

Hard to say: Since ovarian cancer often goes undiagnosed for quite a while it can present very in very advanced stage. The symptoms are vague and often put off as something else. Most patients with ovarian cancer live two years or less.

Neither: Ovarian cancer is rather aggressive in nature and grows fast (although not as fast as other aggressive tumor types). Treatment is initially with surgical resection to minimal disease followed by adjuvant chemotherapy.