**Core Concept**
Male breast cancer (MBC) prognosis is influenced by various factors, similar to female breast cancer. However, due to its rarity, the impact of certain factors might differ. The underlying principle is that a comprehensive evaluation of tumor characteristics and patient-specific factors helps determine the prognosis.

**Why the Correct Answer is Right**
Prognosis in male breast cancer primarily depends on the tumor size, lymph node involvement, and the presence of hormone receptors (ER and PR). The mechanism of hormone receptor expression in male breast cancer is similar to female breast cancer, with a significant proportion of tumors being ER-positive. The presence of HER2 overexpression also impacts the prognosis. Accurate assessment of these factors, often through immunohistochemistry and molecular testing, guides treatment decisions and predicts patient outcomes.

**Why Each Wrong Option is Incorrect**
**Option A:** While age can be a factor in breast cancer prognosis, it is not the primary determinant in male breast cancer.

**Option B:** Although smoking has been linked to an increased risk of various cancers, it is not a direct prognostic factor in male breast cancer.

**Option C:** While obesity can impact the risk and outcomes of various cancers, its influence on male breast cancer prognosis is not as significant as other factors like tumor characteristics.

**Clinical Pearl / High-Yield Fact**
Remember that male breast cancer often presents at an advanced stage due to a delay in diagnosis. A high index of suspicion, especially in older men, is crucial for early detection and improved prognosis.

**Correct Answer: C. Tumor size, lymph node involvement, and hormone receptor status.**