**Core Concept**
Carcinoma endometrium staging involves assessing the extent of tumor spread beyond the uterus. The International Federation of Gynecology and Obstetrics (FIGO) staging system is widely used for this purpose.

**Why the Correct Answer is Right**
When a carcinoma endometrium spreads to the superficial inguinal lymph nodes, it indicates regional lymph node involvement. According to the FIGO staging system, this would classify the cancer as stage III. Specifically, stage III is divided into subcategories, and involvement of the inguinal lymph nodes would fall under stage IIIc.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the involvement of the superficial inguinal lymph nodes in the staging of carcinoma endometrium.
**Option B:** This option is incorrect because it would imply a different extent of lymph node involvement, which is not consistent with the given scenario.
**Option D:** This option is incorrect because it would indicate a more advanced stage of cancer, which is not supported by the information provided.

**Clinical Pearl / High-Yield Fact**
The FIGO staging system for carcinoma endometrium is crucial for determining prognosis and guiding treatment decisions. It is essential to accurately assess the extent of tumor spread to assign the correct stage.

**Correct Answer: C. Stage IIIc.**