Epidemiology
Etiology
Types of breast cancer
Noninvasive carcinomas
Ductal carcinoma in situ (DCIS)
- Characteristics
- No penetration of the basement membrane
- Preceded by ductal atypia
- Frequently appears as a pattern of grouped microcalcifications on mammography
- Higher risk of subsequent ipsilateral invasive carcinoma
- Comedocarcinoma
- Characteristics: subtype of DCIS characterized by central necrosis
Tip
Noninvasive carcinomas are characterized by the absence of stromal invasion.
Invasive carcinomas
Invasive ductal carcinoma (IDC)
- Characteristics
- Most common type of invasive breast cancer (∼ 80%)
- Aggressive formation of metastases
- Localization
- Unilateral
- Mostly unifocal
Medullary breast cancer
- Characteristics
- Rare subtype of invasive ductal carcinoma
- Most common tumor associated with the BRCA1 mutation
- Well-circumscribed soft tumor with smooth borders (may appear benign)
- Usually triple-negative
- Lymphadenopathy
- Differential diagnosis: fibroadenoma
Invasive lobular carcinoma (ILC)
- Characteristics
- ∼ 10% of all invasive breast carcinomas
- Less aggressive than ductal carcinoma
- Localization
- Bilateral in ∼ 20% of cases
- Frequently multifocal
Clinical features
Locally advanced disease
- Skin
- Retractions or dimpling (due to fixation to the pectoral muscles, deep fascia, Cooper ligaments, and/or overlying skin)
- Peau d’orange (see below)
Subtypes and variants
Paget disease of the breast
- Definition: a rare type of breast cancer that affects the lactiferous ducts and the skin of the nipple and areola
- Pathogenesis: migratory/epidermotropic theory: neoplastic ductal epithelial cells from an underlying DCIS or IDC move through the lactiferous ducts and invade the surrounding epidermis of the nipple.
- Clinical features
- Erythematous, scaly, or vesicular rash affecting the nipple and areola
- Pruritus; burning sensation
- Nipple retraction
- Ulceration that causes blood-tinged nipple discharge
- Diagnostics
- Punch/wedge or surface biopsy of nipple tissue: Paget cells confirm disease.
Inflammatory breast cancer (IBC)
- Definition: a rare form of advanced, aggressive invasive carcinoma characterized by dermal lymphatic invasion of tumor cells
- Clinical features
- Peau d’orange
- Erythematous, warm, and edematous skin plaques with prominent hair follicles that resemble orange peel
- Caused by obstruction of the lymphatic channels due to tumor growth
- Tenderness, burning sensation
- Blood-tinged nipple discharge
- Signs of metastatic disease (e.g., axillary lymphadenopathy)
- Usually no palpable mass
- Peau d’orange
- Differential diagnosis
- Mastitis
- Fever
- No Peau d’orange
- Good response to antibiotics
- Paget disease of the breast
- Breast abscess
- Mastitis
Tip
It is called inflammatory breast cancer because its appearance resembles inflammation, but there is actually no inflammation!
Diagnostics
Receptor testing
- Hormone receptors (HR) positive
- Estrogen receptor
- Progestogen receptor
- Human epidermal growth factor receptor 2 (HER2/neu, c-erbB2) positive
- Triple negative
Prognosis
- Hormone-negative breast cancer has a poorer prognosis than hormone-positive breast cancer.
- HER2-positive tumors show aggressive growth and metastasize quickly compared to HER2-negative tumors.
- Triple-negative disease is associated with a poor prognosis.