What is the cause of abnormal vaginal bleeding due to the cause of Epithelial Ovarian Cancer?

As a student, i am doing a report on Epithelial Ovarian Cancer.
But there are somethings that i do not understand.
The common symptoms while diagnosed with Epithelial Ovarian Cancer are:
- low abdomen pain,
- abnormal vaginal bleeding and
- abnormal mensturation cycle.
Well...What i don't get is how does the cancer causes these symptoms.

Could someone help me out with that?
Thanks a lot

[nyc lady]

The symptoms of ovarian cancer, regardless of the type are vague, but, exist.  They are also the same symptoms as many other conditions, thus, if they exist more than 2 weeks, we urge all women to seek medical attention, preferrably by a gynocologist.  The symptoms include:
1) feeling of fullness
2) bloating
3) change in  urination/bowel patterns
4) fatigue
5) change in abdominal girth
6) indigestion