**Core Concept**
Prognostic stage groups in breast carcinoma are determined by factors that influence tumor behavior, spread, and response to therapy. These include tumor size (T), histological grade, and HER-2 status, which provide direct biological and pathological insights into disease aggressiveness.

**Why the Correct Answer is Right**
Tumor size (T), histological grade, and HER-2 status are all integral components of the TNM staging system and are used to predict prognosis and guide treatment. Grade reflects cellular differentiation and growth rate, HER-2 status indicates receptor-driven tumor biology, and tumor size correlates with local extent and lymph node involvement. Age, while relevant to overall health and comorbidities, is not a direct prognostic factor in the formal staging or risk stratification of breast cancer.

**Why Each Wrong Option is Incorrect**
Option A: Tumor size is a key component of TNM staging and directly affects prognosis.
Option B: Grade reflects biological aggressiveness and is used in risk assessment models like the Nottingham grade.
Option C: HER-2 status is a major biomarker that predicts response to targeted therapies and prognosis.

**Clinical Pearl / High-Yield Fact**
In breast cancer, HER-2 status and tumor grade are used in clinical decision-making for therapy selection and risk prediction, while age is considered a modifier of treatment tolerance rather than a standalone prognostic factor.

✓ Correct Answer: D. Age