Which of the following conditions is characterized by the presence of external endometrial tissue?

• A. Uterine fibroids
• B. Polycystic ovarian syndrome
• C. Endometriosis
• D. Ovarian cancer

Answer: (C)

Endometriosis is a condition where endometrial tissue, which normally lines the inside of the uterus, grows outside of the uterus. This can involve various pelvic organs, such as the ovaries, fallopian tubes, and the surface of the pelvic lining. The presence of this tissue outside the uterus can lead to inflammation, pain, and scarring as well as other symptoms such as heavy menstrual bleeding and fertility issues.

In contrast, uterine fibroids are benign growths composed of muscular tissue that develop within the uterine wall, and they do not involve endometrial tissue outside the uterus. Polycystic ovarian syndrome (PCOS) is a hormonal disorder characterized by multiple ovarian cysts, irregular menstrual cycles, and metabolic issues, but it does not involve the external presence of endometrial tissue. Ovarian cancer refers to cancer that originates in the ovaries, which is a separate pathological condition and does not involve endometrial tissue being present outside the uterus.

Therefore, the defining characteristic of endometriosis being the abnormal location of endometrial-like tissue is what makes it the correct answer in this context.