**Core Concept**
The question requires the application of FIGO (International Federation of Gynecology and Obstetrics) staging system for endometrial cancer, specifically for a perimenopausal lady with advanced disease features.

**Why the Correct Answer is Right**
The given clinical scenario suggests stage IVB endometrial cancer, characterized by vaginal and inguinal lymph node metastases. The presence of more than half myometrial invasion indicates high-risk disease, but the key factor leading to stage IVB is the distant metastasis to the lymph nodes and vagina. The FIGO staging system primarily focuses on the extent of myometrial invasion and the presence of cervical or vaginal involvement, but distant metastases are considered for stage IVB.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately reflect the clinical scenario provided. The presence of vaginal and inguinal lymph node metastases is more consistent with stage IVB, rather than stage III.
**Option B:** This option is incorrect as it does not account for the distant metastases to the vagina and inguinal lymph nodes, which are crucial for assigning stage IVB.
**Option C:** This option is incorrect as it does not accurately reflect the clinical scenario provided. The presence of more than half myometrial invasion and distant metastases to the vagina and inguinal lymph nodes is more consistent with stage IVB, rather than stage IIIA.

**Clinical Pearl / High-Yield Fact**
When evaluating endometrial cancer, it is essential to consider the FIGO staging system to accurately assess prognosis and guide treatment decisions. The presence of distant metastases, such as vaginal and inguinal lymph node involvement, is a critical factor in determining the stage of disease.

**Correct Answer:** D. Stage IVB.