MRI features most consistent with a large intramural leiomyoma with central cystic degeneration.

When the leiomyoma increases in size, the vascular supply to it becomes inadequate and leads to different types of degeneration: hyaline, cystic, myxoid, or red degeneration. Hyalinization is the commonest type of degeneration. Cystic degeneration is an uncommon type and represents ~4% of all types of uterine leiomyoma degeneration.