Breast Immunohistochemistry (IHC)
Sample Type: Tissue (Formalin-fixed, paraffin-embedded biopsy or surgical specimen)

Overview
Breast Immunohistochemistry (IHC) is a laboratory technique used to detect specific protein markers in breast tissue using antibodies. It plays a vital role in the diagnosis, classification, and management of breast cancer. By identifying the expression of certain proteins, IHC helps determine the tumor subtype, prognosis, and the most effective treatment options.

Key Markers in Breast IHC
Estrogen Receptor (ER)

Indicates hormone sensitivity; positive tumors may respond to hormonal therapy.

Progesterone Receptor (PR)

Often co-expressed with ER; also predicts hormone therapy response.

HER2/neu (Human Epidermal Growth Factor Receptor 2)

Overexpression suggests a more aggressive tumor; HER2-positive cancers may benefit from targeted therapy (e.g., trastuzumab).

Ki-67

A proliferation marker used to assess tumor aggressiveness.

p53, E-cadherin, GATA3, and others

Used for further classification and differential diagnosis.

Clinical Applications
Diagnosis: Helps confirm malignancy and differentiate types of breast tumors.

Prognosis: Marker expression correlates with tumor behavior and outcome.

Treatment: Guides targeted therapies (e.g., endocrine therapy, HER2-targeted therapy).

Subtyping: Assists in categorizing breast cancer into Luminal A, Luminal B, HER2-enriched, and Triple-negative types.

Procedure
Tissue sections from biopsies or surgeries are treated with specific antibodies against target proteins. A visible reaction, typically color change, indicates the presence and level of marker expression.

Advantages
Precise tumor characterization

Personalized treatment planning

Widely available and relatively cost-effective

Limitations
Requires high-quality tissue processing

Interpretation depends on pathologist expertise

Some tumors show heterogeneous expression

Conclusion
Breast Immunohistochemistry is an indispensable tool in modern breast cancer management, allowing for accurate diagnosis, prognosis, and selection of targeted treatments through detection of critical biomarkers.