**Core Concept:** Ovarian tumors can be benign or malignant, with malignant ones having a higher risk of complications. Ovarian cancer is the most common cause of death from gynecologic malignancies.

**Why the Correct Answer is Right:** Ovarian cancer is the most common malignant tumor in the female genital system, and its complications can be life-threatening. Ovarian cancer can invade surrounding structures and spread to distant organs, leading to various complications.

**Why Each Wrong Option is Incorrect:**

A. Müllerian duct remnants (Müllerian adenosis): This is a benign condition and not a significant complication of ovarian tumors.
B. Ovarian cysts: Cysts are generally benign and do not pose significant complications unless they rupture or become huge.
C. Ovarian torsion: While ovarian torsion can lead to pain and acute abdomen, it is not a direct complication of ovarian tumors but rather an injury to the ovary.
D. Endometriosis: Endometriosis is a condition where endometrial tissue grows outside the uterus, not a direct complication of ovarian tumors.

**Clinical Pearl:** Early detection and management of ovarian cancer are crucial to improve prognosis and reduce complications. Regular gynecological examinations and timely imaging studies are essential in detecting ovarian cancer at an early stage.

**Correct Answer:** .