<s>[INST] context: Adenomyosis is a condition in which normal endometrial glands grow into the myometrium. The symptomatic disease primarily occurs in multiparous women over the age of 35 years, compared to endometriosis, in which onset is considerably younger. Patients with adenomyosis complain of dysmenorrhea and menorrhagia, and the classical examination findings include a tender, symmetrically enlarged uterus without adnexal tenderness. Although patients with endometriosis can have similar complaints, the physical examination of these patients more commonly reveals a fixed, retroveed uterus, adnexal tenderness and scarring, and tenderness along the uterosacral ligaments. Leiomyoma is the most common pelvic tumor, but the majority are asymptomatic and the uterus is irregular in shape. Patients with endometritis can present with abnormal bleeding, but endometrial biopsies show an inflammatory pattern. Uterine sarcoma is rare and presents in older women with postmenopausal bleeding and nontender uterine enlargement. [/INST] question: A 39- year old woman, G3P3, complains of severe, progressive secondary dysmenorrhea and menorrhagia. Pelvic examination demonstrates a tender, diffusely enlarged uterus with no adnexal tenderness. Endometrial biopsy is normal. This patient most likely has | options: A: Endometriosis B: Endometritis C: Adenomyosis D: Uterine sarcoma | answer: C </s>