creation date: 2026-01-05 21:57
tags: PathologiesIncomplete
Breast Cancer
Background
Definitions
Breast cancer is the most common cancer diagnosed in women and most common cause of death among cancers among women worldwide.
Invasive breast cancer is characterized by invasion of neoplastic cells beyond the basement memebrane.
Etiology and Risk Factors
Breast cancer most commonly arises in the ductal epithelium (ie. ductal carcinoma) but can also develop in the breast lobules (ie. lobular carcinoma).
Well-established risk factors include:
- Age 50 or older
- Benign breast disease, especially cystic disease, proliferative types of hyperplasia, and atypical hyperplasia
- Exposure to ionizing radiation
- First childbirth after age 20
- Higher socioeconomic status
- History of breast cancer
- History of breast cancer in a first-degree relative
- Hormone therapy
- Nulliparity
- Obesity (BMI ≥30, increases by 3% every 1 BMI increase)
Probable risk factors include:
- Alcohol consumption
- Did not breastfeed
- Elevated endogenous estrogen levels
- High BMI*
- Hormonal contraception therapy
- Increased mammographic density of breast tissue
- Menarche before age 12
- Menopause after age 45
- Mutations in BRCA 1 and BRCA 2 genes
Types
Molecule subtypes
Breast cancers can be categorized by the molecular subtype which often guides treatment and prognosis.
- Luminal A: Hormone receptor positive, human epidermal growth factor receptor (HER)-2 negative
- Luminal B: Hormone receptor positive, HER-2 positive
- Basal-like: Hormone receptor and HER-2 negative
- HER-enriched: Hormone receptor negative, HER-2 positive
Luminal A and B are less aggressive and have better prognosis. HER-enriched are more aggressive but prognosis is generally better with targeted anti-HER therapy. Basal-like tumours tend to have a worse prognosis with poor survival.
Histological variants
Ductal adenocarinoma
- 50-75% of BC
- Arises from terminal duct-lobular unit with abnormal epithelial cells
- No pathognomonic histologic feature
Lobular carcinoma - 10-15% of BC
- Often clinically occult until disease is extensive
- Multifocal tumours and bilateral disease common
Mucinous carcinoma - 2-5% of BC
- Well-demarcated in older women
- Characterized by mucin production
Tubular carcinoma - 1-2% of BC
- Small glands and tubules form from infiltrating cells
Medullary carcinoma - Aggressive and poorly differentiated
- More common in BRCA mutant and younger patients
Clinical Presentation
Signs & Symptoms
In most patients, breast cancer is asymptomatic with masses found incidentally or by screening.
Findings may include:
- Palpable lump
- Breast pain
Advanced disease may present with:
- Peau d’orange
- Frank ulceration
- Axillary lymphadenopathy
- Signs of distant metastasis
Inflammatory breast cancer may be features similar to breast abscess.
History & Physical Exam
A complete clinical breast exam including lymph node exam should be performed.
Diagnosis
Criteria
Work-up
Screening
Screening is indicated for people aged 40-74 with average risk and people aged 30-69 with high risk. Those over age 74 can be screened but should make individualized decision.
High risk is:
- Gene mutation that increases risk (eg. BRCA1, BRCA2, TP53, PALB2)
- First-degree relative of someone with genetic risk
- Personal or family history of breast or ovarian cancer
- Radiation therapy to chest to treat another cancer or condition before age 30 and at least 8 years ago
Screening consist of mammography every 2 years.