Could a benign cyst in my fallopian tube have caused my ectopic pregnancy?

Not likely: Fallopian tube cysts called hydatid cysts of morgagni actually occur at the end and outside of the tube. They usually have a thin stalk with a bleb of fluid surrounded by a thin cyst wall. There are little finger like projections in the tube that move the egg along. The most common known cause of ectopics outside of spontaneous ones (no cause) is exposure to chlamydia.