**Core Concept**
The prognosis of carcinoma breast is determined by several factors, including tumor size, lymph node involvement, and hormone receptor status. However, one factor stands out as the most important prognostic indicator.

**Why the Correct Answer is Right**
The most important prognostic factor for carcinoma breast is lymph node status, as it reflects the tumor's ability to metastasize. The presence of lymph node metastases indicates a higher stage of cancer and a poorer prognosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Tumor size is a significant factor, but not the most important.
**Option C:** Hormone receptor status is crucial for treatment, but not the most critical prognostic factor.

**Clinical Pearl / High-Yield Fact**
Lymph node status is a key determinant of prognosis in breast cancer, and its evaluation is essential for staging and treatment planning.

**Correct Answer:** D. Lymph node status.