Molecular classification of breast cancer is based on –
**Core Concept**
Molecular classification of breast cancer involves categorizing tumors based on their genetic and molecular characteristics, which helps in understanding the tumor's behavior, predicting prognosis, and guiding treatment decisions.
**Why the Correct Answer is Right**
The molecular classification of breast cancer is primarily based on the hormone receptor status (estrogen receptor (ER) and progesterone receptor (PR)) and the presence or absence of human epidermal growth factor receptor 2 (HER2) amplification. This classification helps in identifying the intrinsic subtypes of breast cancer, which are luminal A, luminal B, HER2-enriched, and basal-like (triple-negative). The luminal A subtype is characterized by the presence of ER and PR, whereas the luminal B subtype is ER-positive but PR-negative or weakly positive. The HER2-enriched subtype is characterized by HER2 amplification, and the basal-like subtype lacks ER, PR, and HER2 expression.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not mention the hormone receptor status and HER2 amplification, which are the primary molecular characteristics used for breast cancer classification.
**Option B:** This option is incorrect because it does not specify the molecular characteristics and is too vague. While genetics play a role in breast cancer, the molecular classification is more specific than just genetics.
**Option C:** This option is incorrect because it is not a recognized classification system for breast cancer. While histological grading is an important aspect of breast cancer diagnosis, it is not the same as molecular classification.
**Clinical Pearl / High-Yield Fact**
The molecular classification of breast cancer is crucial for guiding treatment decisions, and patients with HER2-positive breast cancer may benefit from targeted therapies such as trastuzumab.
**Correct Answer: C. Histological grading.**