Breast Carcinoma
Breast cancer is the most common cancer in women. Understanding the histological classification and molecular markers is essential for both diagnosis and targeted therapy.
1. Histological Classification
| Type | Key Features |
|---|---|
| DCIS | Ductal Carcinoma In Situ; fills the ductal lumen. E-cadherin positive. |
| Invasive Ductal | Most common invasive type. “Rock-hard” mass; duct-like structures. |
| Invasive Lobular | “Indian file” cells. Loss of E-cadherin (signet ring cells). |
2. Molecular Markers (The “Big Three”)
- ER/PR (Estrogen/Progesterone Receptor): Positive tumors respond to endocrine therapies like tamoxifen.
- HER2/neu: Overexpression indicates aggressive behavior but susceptibility to trastuzumab (Herceptin).
- Triple-Negative: ER-, PR-, and HER2-. Highly aggressive, more common in BRCA1 mutation carriers.
3. Exam Must-Knows
- Paget Disease: Eczematous patches on the nipple; indicates underlying DCIS or invasive cancer.
- Inflammatory Breast Cancer: “Peau d’orange” (dimpling) due to lymphatic obstruction. Highly aggressive (poor prognosis).
Pathology Board Hint: Remember: Invasive Lobular = E-cadherin loss = “Indian file” arrangement. Invasive Ductal = Desmoplastic reaction (“rock-hard”). Paget’s disease of the nipple is not just a skin condition; it is almost always linked to underlying malignancy.