**Core Concept**
The management of carcinoid tumors of the appendix requires consideration of the tumor's size, location, and potential for metastasis. In general, tumors larger than 2 cm have a higher risk of lymph node metastasis and may require a more extensive surgical resection.

**Why the Correct Answer is Right**
A 2.5-cm tumor at the base of the appendix is considered an intermediate-sized tumor. Given its size and location, there is a higher risk of lymph node involvement. Right hemicolectomy is the recommended surgical procedure for such tumors, as it allows for the removal of the tumor, the involved lymph nodes, and a portion of the small intestine. This procedure is more extensive than simple appendectomy but less than segmental ileal resection or cecectomy.

**Why Each Wrong Option is Incorrect**
**Option A:** Appendectomy alone is insufficient for a tumor of this size, as it does not address the potential for lymph node metastasis.

**Option B:** Segmental ileal resection is a more limited procedure that may not adequately address the tumor's potential spread to lymph nodes in the cecum or beyond.

**Option C:** Cecectomy, or removal of the cecum, may not be sufficient to address potential lymph node involvement in the ileum or more distal small intestine.

**Clinical Pearl / High-Yield Fact**
The key to managing carcinoid tumors of the appendix is to consider the tumor's size and location. Tumors larger than 2 cm or those with lymph node involvement may require more extensive surgical resection, such as right hemicolectomy.

**Correct Answer:**
✓ Correct Answer: D. Right hemicolectomy