**Core Concept**
The staging of endometrial carcinoma is based on the International Federation of Gynecology and Obstetrics (FIGO) system, which takes into account the extent of myometrial invasion, cervical involvement, and the presence of lymph node metastasis, among other factors.

**Why the Correct Answer is Right**
The presence of >50% myometrial invasion and vaginal metastasis indicates a more advanced disease. However, the absence of pelvic and retroperitoneal lymph node involvement is a crucial factor in determining the stage. The presence of peritoneal seedings is a significant adverse prognostic factor. According to the FIGO staging system, the presence of peritoneal seedings is classified as stage IVB, regardless of the extent of myometrial invasion or lymph node involvement.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not account for the presence of peritoneal seedings, which is a critical factor in determining the stage of endometrial carcinoma.
**Option B:** This option is incorrect as it incorrectly assigns a stage that does not reflect the presence of peritoneal seedings.
**Option C:** This option is incorrect as it does not accurately reflect the FIGO staging system for endometrial carcinoma.

**Clinical Pearl / High-Yield Fact**
Remember that the FIGO staging system for endometrial carcinoma emphasizes the importance of peritoneal seedings as a significant adverse prognostic factor, which can elevate the stage to IVB, even in the absence of lymph node involvement.

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