A serous cystadenoma of the ovary is seldom so well manifested as in this case. This huge cystic lesion had this solitary septum with a vessel well seen on Power Doppler. See more ultrasound images of this case at:
Here you will find a sonographic pictorial review a variety of cystic masses (cysts) of the ovaries. Among them are mucinous cystadenoma and cystadenocarcinoma and calcific masses like dermoid cyst.
On the parent page at:
there are interesting ultrasound pictures of functional cysts of the ovaries, hemorrhagic ovarian cysts and the bane of modern women: chocolate cyst or endometrioma of ovary.