**Core Concept**
Duke's staging system is a classification system used to determine the extent of spread of esophageal cancer. It is divided into three stages: A (tumor limited to the mucosa), B (tumor invades the muscularis propria), C (tumor invades through the muscularis propria into periesophageal tissues), and further subdivided into three sub-stages: C1 (tumor invades through the muscularis propria into periesophageal tissues without lymph node metastases), C2 (tumor invades through the muscularis propria into periesophageal tissues with regional lymph node metastases).

**Why the Correct Answer is Right**
Duke's stage C2 refers to carcinoma with regional lymph node metastases. This means that the cancer has spread from the esophagus to nearby lymph nodes, but not to distant parts of the body. The presence of regional lymph node metastases indicates a more advanced stage of cancer.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because Duke's stage A refers to carcinoma limited to the mucosa.
* **Option B:** This is incorrect because Duke's stage C1 refers to carcinoma that invades through the muscularis propria into periesophageal tissues without lymph node metastases.
* **Option C:** This is incorrect because Duke's stage C is a broader category that includes both C1 and C2 sub-stages.

**Clinical Pearl / High-Yield Fact**
When evaluating esophageal cancer, it's essential to know the extent of spread to determine the best course of treatment and prognosis.

**Correct Answer:** C. Carcinoma with regional lymph node metastases.