Breast - General

Anatomy
Sits atop the pectoralis muscles (invasion of the pectoralis does not count as chest wall invasion for T4 disease). Pec minor attaches at coracoid process and ribs 3, 4, and 5
Most breast tumors develop at the interface between ducts and lobules ("terminal ductal lobular unit")
Most common location is the axillary tail
Cooper's ligaments are connective tissue within the breast parenchyma; involvement can cause skin dimpling even if the skin is not actually involved

Lymph node drainage
Axillary levels I, II, III (demarcated by pec. minor; Level III is medial, II under the muscle, I lateral)
Infrapectoral or Rotter's nodes
Supraclavicular nodes (usually involved only after the axilla is involved)
Internal mammary nodes (medial/central/inferior tumors)
A standard axillary dissection removes levels II and III
Risk of axillary involvement depends on tumor size, grade, and patient age
Internal mammary risk depends on tumor size, location, + axillary nodes
Supraclavicular risk depends on number of axillary nodes involved (4 or more), involvement of the apex of the axilla, tumor grade, extracapsular extension

Epidemiology
Most common cancer in US women: 210,000 invasive cases, 60,000 in situ cases, 40,000 deaths
Screening has been associated with a large increase in cases in the US in the 1990's
Male breast cancer - 1700 cases, 460 deaths
Mortality from breast cancer is decreasing

Risk factors
1) Age*
2) Estrogen excess (early menarche, late menopause, nulliparity, older age at first pregnancy, HRT)
3) Personal history of breast cancer
4) Family history of breast cancer
5) Personal history of atypical ductal hyperplasia
6) RT to chest (especially during adolescence)
7) Obesity
8) Alcohol

Risk factors for bilateral disease
1) Invasive lobular histology
2) Age
3) + family history
4) Multicentric disease
5) Parity
6) PR+
7) High grade tumors

Genetic syndromes associated with breast cancer
1) Li-Fraumeni syndrome
-p53 mutation
-Breast cancer is the most common malignancy in Li-Fraumeni patients (up to 90% risk)
2) BRCA-1
-65-85% lifetime breast cancer risk
-50% ovarian cancer risk
-Increased rates of colon and prostate tumors
-Associated with triple negative (basal) phenotype
3) BRCA-2
-Similar 65-85% breast cancer risk as BRCA-1 patients
-Also have elevated risk of ovarian cancer, but less so than BRCA-1
-Associated with pancreatic cancer, male breast cancer

BRCA 1 and 2 mutated patients account for 5-10% of all breast cancer cases

Chemoprevention
Tamoxifen: NSABP P-1
-Decreased risk of invasive and in situ cancer by 50% vs. placebo in women with a Gail model risk of 1.67% in 5 years or who had LCIS
-Raloxifene vs. tamoxifen: NSABP P-2

-Equal to tamoxifen in ability to prevent breast cancer

-Fewer adverse events: VTE, uterine cancer, cataract surgery all decreased in raloxifene group

Birads criteria

0 = further imaging recommended

1 = no mammographic abnormality

2 = benign abnormality

3 = likely benign abnormality; short follow up recommended

4 = suspicious abnormality, biopsy recommended

5 = highly suspicious abnormality

6 = biopsy proven cancer

Radiographic findings suggestive of malignancy

Calcifications: 100-300um; rodlike, tubular, branching, punctate; clustered microcalcifications

Spiculated mass

Hypoechoic mass (on u/s)

Contralateral breast cancer is found in 1-2% of patients

Workup

All patients: B/L mammogram and ultrasound; +/- MRI

MRI is more useful in younger patients or women with dense breasts

Imaging of the breast is followed by guided core needle biopsy

For DCIS patients: no further staging is needed if DCIS alone confirmed at lumpectomy

For early-stage invasive patients: staging is completed by chest x-ray, CBC, CMP; tumor excision and sentinel mymph node biopsy

For locally advanced patients: CT of chest/abdomen/pelvis or PET scan; bone scan; CBC/CMP; brain MRI considered if neurologic symptoms or mets elsewhere; neoadjuvant chemo often given (more later)