A 50-year-old female patient complains of aching pain in the lower abdomen. She has a history of normal menstrual cycle. At the age of 40, the patient underwent a surgery for gastric ulcer. Examination findings: abdomen is soft, in the hypogastrium there is a well-defined nodular tumor of limited mobility. Vaginal examination findings: the cervix is clean, of cylindrical shape. Body of the uterus cannot be palpated separately. On both sides of the uterus palpation reveals tight tumors with an uneven surface. The tumors are immobile andl fill the whole pelvic cavity. What is the most likely diagnosis?