Unusual findings for a supposed ovarian cancer.
Actually the main lesion originates from the subperitoneal space: it most likely comes from the perineum, breaks through the puborectal and levator ani muscles, extends into the right ischiorectal fossa and pushes to the left the rectum, uterus and bladder, without invading them. It then most likely extends in the retroperitoneal space up to the upper abdomen, behind the liver. The right colon is pushed away to the left, actually the entire digestive tract is pushed away as a whole.
The lesion features mostly a liquid-like content, probably myxoid, (NOT ascites), T2 hyperintense, T1 hypointense with small T1FS hyperintense spots (blood or proteins), without fat.
Interestingly there are long thin "filaments" enhancing after contrast injection. These are oriented vertically in a layered "onion-peel"-like fashion.