The investigation of choice in a 55-year-old postmenopausal woman who has presented with postmenopausal bleeding is:
**Core Concept**
The investigation of choice in a postmenopausal woman with postmenopausal bleeding is crucial due to the high risk of endometrial cancer. Endometrial cancer is the most common gynecologic malignancy in postmenopausal women, and early detection is key to improving outcomes.
**Why the Correct Answer is Right**
The correct investigation is an **Endometrial Biopsy** (Option C). This is because endometrial biopsy allows for direct sampling of the endometrium, enabling the detection of cancerous cells, precancerous changes, or other abnormalities. It is a minimally invasive procedure that can be performed in an outpatient setting, making it an ideal choice for initial evaluation. The procedure typically involves inserting a catheter or cannula through the cervix and into the endometrial cavity, followed by the collection of tissue samples for histopathological examination.
**Why Each Wrong Option is Incorrect**
* **Option A:** Pap smear is not the investigation of choice for postmenopausal bleeding. While a Pap smear can detect cervical cancer and precancerous changes, it is not sensitive for endometrial cancer.
* **Option B:** Transvaginal ultrasound (TVUS) can be used to evaluate the endometrial thickness and detect endometrial polyps or cancer. However, it is not the definitive investigation for postmenopausal bleeding. A biopsy is still required to confirm the diagnosis.
* **Option D:** Hysteroscopy can be used to visualize the uterine cavity and detect abnormalities such as polyps or cancer. However, it is typically used for diagnostic or therapeutic purposes after an abnormal biopsy result.
**Clinical Pearl / High-Yield Fact**
The American College of Obstetricians and Gynecologists (ACOG) recommends that postmenopausal women with bleeding should undergo an endometrial biopsy as the initial investigation, regardless of the bleeding pattern or duration.
**Correct Answer: C. Endometrial Biopsy**