What is the difference between ovarian cyst and tumor?

Any growth is tumor: A cyst is one type of tumor which, by definition is a fluid filled structure. This is different than a solid growth which is more often cancerous. But most ovarian cancers are cystic. So you should seek advice from your gynecologist and make sure this cyst is not cancerous(size matters in this regard....Benign cysts are small...2-4 cm in size...Bigger ones are more likely to be cancerous).