**Core Concept**
The management of postmenopausal vaginal bleeding (PMVB) involves assessing the risk of endometrial cancer, with endometrial thickness being a key factor. An endometrial thickness of 8.0 mm in a postmenopausal woman is considered abnormal and warrants further evaluation.

**Why the Correct Answer is Right**
Given the abnormal endometrial thickness, the next step in management is to obtain an endometrial sample for histopathological examination. This is typically done via endometrial biopsy or dilation and curettage (D&C). The procedure helps to rule out endometrial hyperplasia or cancer, which are common causes of PMVB. The sample is then examined for cellular abnormalities, such as atypia or malignancy.

**Why Each Wrong Option is Incorrect**
**Option A:** Performing a pelvic ultrasound with Doppler flow studies may provide additional information on blood flow to the endometrium, but it does not directly address the need for histopathological examination.
**Option B:** Starting hormone replacement therapy (HRT) without evaluating the cause of vaginal bleeding may mask symptoms but does not rule out underlying malignancy.
**Option C:** Conducting a Pap smear is not relevant in this scenario, as it is primarily used for cervical cancer screening, not endometrial cancer.

**Clinical Pearl / High-Yield Fact**
In postmenopausal women with vaginal bleeding, an endometrial thickness of ≥5 mm is considered abnormal and warrants further evaluation.

**Correct Answer:** C. Dilation and curettage (D&C) to obtain an endometrial sample for histopathological examination.