A 48-year-old woman complains that within the last 8-9 months she had very heavy periods that impair her ability to work. For 2 years, her health has been monitored by a gynecologist for uterine fibroids. Objectively, her cervix is cylindrical, clean, the cervical opening is closed; the body of the uterus is enlarged up to 9-10 weeks of pregnancy, firm, mobile, and painless; the appendages on both sides cannot be determined; the parametria are free; the fornices are deep; mucous discharge is being produced. What is the most likely diagnosis in this case?