What can cause a cyst on the fallopian tube?

Unknown: Some women have cysts that develop on or around the fallopian tubes. Usually they are very small but sometimes they can be large. Often they are filled with water and are not harmful. Most of the time they are accidental findings during surgery for another reason.

Embryologic remnant: Certain para-tubal cysts are embryologic remnants, in other words 'leftover stuff' from when the woman was in utero and her pelvic organs were forming. Males and females embryos both start with 2 sets of internal ducts: one is intended to develop in males and the other in females. Leftovers from either duct can be present as cysts near the fallopian tube.

CAN'T CAUSE ONE.: It just happens, can't identify a cause. A cyst is a collection of fluid that forms in the and enlarges it in a particular area.