Breast Cancer: Types, Causes & Essential Lab Tests

Breast cancer is one of the most common cancers affecting women worldwide. It occurs when the cells in the breast begin to grow uncontrollably, forming a tumor that can invade surrounding tissues or spread to other parts of the body.

Understanding the types, causes, and laboratory investigations of breast cancer is crucial for early detection and effective treatment.

Types of Breast Cancer

Breast cancer is broadly categorized into three main types based on its origin:

1. Invasive Ductal Carcinoma (IDC): This is the most common type of breast cancer, accounting for about 80% of all cases. IDC begins in the milk ducts and can spread to nearby tissues.
2. Invasive Lobular Carcinoma (ILC): The second most common type, ILC starts in the milk-producing lobules of the breast and can spread to other areas.
3. Ductal Carcinoma In Situ (DCIS): DCIS is a non-invasive or pre-invasive form of breast cancer. It starts in the milk ducts but has not spread beyond the ducts into the surrounding breast tissue. It is considered an early form of breast cancer and is highly treatable.

There are also less common types of breast cancer, including:

• Triple-Negative Breast Cancer: Lacks estrogen receptors (ER), progesterone receptors (PR), and HER2 protein, making it more difficult to treat.
• HER2-Positive Breast Cancer: Overexpression of the HER2 protein drives the cancer's growth.

Causes and Risk Factors

Breast cancer can be caused by several factors, including:

1. Genetic Mutations: Mutations in certain genes, such as BRCA1 and BRCA2, significantly increase the risk of developing breast cancer. Women with these mutations have a higher lifetime risk, and this form of cancer is often hereditary.
2. Family History: A family history of breast cancer increases the risk, particularly if a first-degree relative (mother, sister, or daughter) has been diagnosed with the disease.
3. Hormonal Factors: Prolonged exposure to estrogen, either due to early menstruation or late menopause, can elevate the risk.
4. Lifestyle Factors: Obesity, lack of physical activity, excessive alcohol consumption, and smoking are lifestyle factors that contribute to breast cancer.
5. Age: The risk of breast cancer increases with age, particularly after the age of 50.

Laboratory Investigations for Breast Cancer

Early detection of breast cancer improves treatment outcomes, and laboratory investigations play a critical role in diagnosing the disease.

Biopsy

A biopsy is the gold standard for diagnosing breast cancer. It involves taking a small sample of tissue from the suspicious area for examination. Types of biopsies include:

• Fine Needle Aspiration (FNA)
• Core Needle Biopsy (CNB)
• Excisional Biopsy

Immunohistochemistry (IHC)

IHC is used to determine hormone receptor status. It evaluates the presence of:

• Estrogen Receptor (ER)
• Progesterone Receptor (PR)

IHC also assesses HER2/neu protein expression, which plays a significant role in aggressive breast cancers. Results help classify breast cancer into hormone receptor-positive or HER2-positive categories, guiding treatment decisions.

BRCA1 and BRCA2 Genetic Testing

Mutations in the BRCA1 and BRCA2 genes are strongly associated with hereditary breast cancer. These genes normally help repair damaged DNA, but when mutated, they lose their ability to prevent cancerous growth.

• BRCA1: Women with a mutation in this gene have up to a 72% lifetime risk of developing breast cancer.
• BRCA2: The risk associated with BRCA2 mutations is slightly lower but still significant, with about a 69% lifetime risk.

Genetic testing for these mutations is recommended for individuals with a strong family history of breast or ovarian cancer. Identifying these mutations can also provide important information for family members who may carry the gene.

Fluorescence in situ hybridization (FISH)

FISH is a specialized test used to detect HER2 gene amplification in breast cancer cells. This test is often done when the IHC results for HER2 are borderline, helping to determine the need for targeted therapies like Trastuzumab.

Treatment and Prognosis

Treatment of breast cancer depends on its type, stage, and receptor status. The main options include:

• Surgery: Lumpectomy or mastectomy.
• Systemic Therapy: Chemotherapy, hormone therapy (for ER/PR-positive cancers), and targeted therapy (e.g., Trastuzumab for HER2-positive cancers).
• Radiation Therapy: Often used after surgery to reduce the risk of recurrence.

Conclusion

Breast cancer is a complex disease with multiple factors influencing its development and progression. Genetic mutations like BRCA1 and BRCA2 play a significant role in hereditary breast cancer, making genetic testing and early diagnosis vital for effective treatment. Laboratory investigations, including biopsy, IHC, mutation analysis, and FISH, are essential tools for accurate diagnosis and personalized treatment planning.

Understanding your risk factors and regularly screening can greatly improve the chances of early detection and successful treatment.