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🎯 Carcinoma Breast - Complete NEET SS Guide

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1. EPIDEMIOLOGY & INCIDENCE

• Most common cancer in women globally (surpassed lung cancer in 2020 with 2.3 million new cases)
• Leading cause of cancer death in females worldwide
• Lifetime risk: 1 in 8 females in the US (living to age 90)
• Incidence highest in North America, Northern/Western Europe, Australia
• In India: incidence is rising; resource-poor countries show 1 in 28 women affected
• ~12% of all new cancer diagnoses globally

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2. RISK FACTORS

Non-Modifiable

Modifiable (Hormonal/Lifestyle)

NEET SS Recall: Increased estrogenic exposure = increased risk. All factors that prolong estrogen stimulation of the breast epithelium are risk factors.

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3. PATHOGENESIS

3A. Familial Breast Cancer (BRCA Pathway)

• BRCA1 (chromosome 17q) and BRCA2 (chromosome 13q) are tumor suppressor genes involved in DNA double-strand break repair (homologous recombination)
• Germline mutations in BRCA1/2 cause ~10% of all breast cancers
• BRCA1-associated cancers tend to be triple negative (ER-/PR-/HER2-), high-grade
• BRCA2-associated cancers are more often ER-positive
• Treatment implication: PARP inhibitors (olaparib) work in BRCA-mutated tumors

3B. Sporadic (Non-Familial) Breast Cancer

• Multistep progression:
  • Normal epithelium → Hyperplasia → Atypical hyperplasia (ADH/ALH) → In situ carcinoma (DCIS/LCIS) → Invasive carcinoma
• Key molecular events:
  • ER/PR positivity: ~70% of breast cancers express estrogen receptor
  • HER2 amplification: HER2/neu (ErbB2) oncogene amplified in ~15-20% → poor prognosis but targetable with trastuzumab
  • TP53 mutations: especially in high-grade and TNBC
  • PIK3CA mutations: found in ER-positive tumors; targetable with PI3K inhibitors

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4. MOLECULAR SUBTYPES (Intrinsic/Gene Expression)

Clinical grouping (used in practice):

• Luminal = ER+/HER2- (hormone receptor positive)
• HER2 = HER2+ (regardless of ER/PR)
• TNBC = ER-/PR-/HER2- (triple negative)

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5. IN SITU CARCINOMAS

5A. Ductal Carcinoma In Situ (DCIS)

• Malignant cells confined within ducts; basement membrane intact (no invasion)
• Most detected by mammography (microcalcifications)
• Subtypes by architecture: comedo, cribriform, micropapillary, solid, papillary
• Comedo type: central necrosis with dystrophic calcification; most aggressive; high-grade
• Risk of progression to invasive carcinoma: if untreated, ~30-50% develop invasive cancer
• Treatment: lumpectomy + radiation ± endocrine therapy (if ER+); mastectomy for extensive disease

5B. Lobular Carcinoma In Situ (LCIS)

• Malignant cells fill and distend the acini of a lobule
• Not palpable, not visible on mammography (no calcification typically)
• Incidental finding in breast biopsies
• Bilateral marker of increased risk in both breasts (~30% lifetime risk of invasive cancer in either breast)
• Lacks E-cadherin expression (E-cadherin negative on IHC) - hallmark finding
• Classic LCIS does NOT require excision; surveillance with or without chemoprevention (tamoxifen)
• Pleomorphic LCIS: aggressive variant - requires excision

Key distinction:

• DCIS = precursor lesion → treat locally
• LCIS = bilateral risk marker → manage bilaterally

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6. INVASIVE BREAST CARCINOMA - HISTOLOGICAL TYPES

Classification (Foote & Stewart):

1. Invasive ductal carcinoma - No Special Type (NST) - ~75-80%
2. Invasive lobular carcinoma - ~10%
3. Medullary carcinoma - ~4%
4. Mucinous (colloid) carcinoma - ~2%
5. Tubular carcinoma - ~2%
6. Papillary carcinoma - ~2%
7. Paget's disease of the nipple
8. Rare types: adenoid cystic, metaplastic, apocrine

6A. Invasive Ductal Carcinoma - NST (Most Common)

• Gross: hard, gritty mass with irregular stellate borders; chalky-white streaks; characteristic grating sound when cut (due to desmoplasia)
• Micro: infiltrating glands/cords/solid nests in desmoplastic stroma; variable grade
• Desmoplastic reaction: tumor cells release FGF, TGFα/β, VEGF → fibrocytes become fibroblasts → collagen deposition → contraction → skin dimpling/nipple retraction

6B. Invasive Lobular Carcinoma

• "Indian file" / single-file pattern of infiltrating cells
• Cells encircle ducts in a targetoid pattern
• E-cadherin negative (same as LCIS - its precursor)
• Bilateral and multicentric more common
• Tends to be ER/PR positive
• Difficult to detect clinically and on mammography (no mass, no calcification)
• More commonly metastasizes to peritoneum, retroperitoneum, leptomeninges, GI tract, ovaries

6C. Medullary Carcinoma

• Well-circumscribed (deceptively benign appearance), soft consistency
• Syncytial growth of large pleomorphic cells
• Dense lymphoplasmacytic infiltrate (TILs) - associated with better prognosis
• Frequently BRCA1-associated, high-grade, triple-negative
• Despite high grade: better prognosis than IDC of similar grade

6D. Mucinous (Colloid) Carcinoma

• Small clusters of tumor cells floating in lakes of extracellular mucin
• Well-circumscribed, gelatinous appearance on gross
• Better prognosis among special types
• Older women; slow-growing

6E. Tubular Carcinoma

• Well-formed tubules with open lumina lined by single layer of cells
• Excellent prognosis - best of all invasive types
• Always low-grade, ER/PR positive

6F. Paget's Disease of the Nipple

• Chronic eczematous eruption of nipple-areola complex → ulceration, weeping
• Pathognomonic: Paget cells - large, pale, vacuolated cells in the rete pegs of nipple epidermis
• Associated with underlying DCIS (always) ± invasive carcinoma
• IHC: CEA positive, CK7 positive; S-100 negative (differentiates from melanoma)
• vs. Pagetoid intraepithelial melanoma: S-100 positive, HMB-45 positive

6G. Inflammatory Breast Carcinoma

• Clinical diagnosis - NOT a histological type
• Rapid onset: breast erythema, warmth, skin thickening, peau d'orange
• Due to dermal lymphatic invasion by tumor emboli
• Most aggressive form of locally advanced breast cancer
• T4d in TNM staging

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7. NOTTINGHAM HISTOLOGIC GRADING (Elston-Ellis Modification)

• Total 3-5 → Grade 1 (well differentiated, best prognosis)
• Total 6-7 → Grade 2 (moderately differentiated)
• Total 8-9 → Grade 3 (poorly differentiated, worst prognosis)

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8. SPREAD OF BREAST CANCER

8A. Local Spread

• Skin involvement → peau d'orange (lymphatic obstruction, not direct invasion)
• Skin dimpling/puckering: shortening of Cooper's ligaments due to desmoplasia
• Nipple retraction: desmoplasia involving subareolar ligaments
• Ulceration: advanced skin invasion
• Chest wall invasion (T4a): pectoralis major, serratus anterior, ribs

8B. Lymphatic Spread (primary route)

• Axillary lymph nodes (most important): drains outer quadrant → Level I → II → III
• Internal mammary nodes: drains inner quadrant/central tumors
• Supraclavicular nodes: N3c (M1 in old staging)
• Axillary nodal status = most important prognostic factor for early breast cancer

• Level I: lateral to pectoralis minor
• Level II: behind pectoralis minor (includes Rotter's nodes between pec major and minor)
• Level III: medial to pectoralis minor (infraclavicular)

8C. Haematogenous Spread

• Neoangiogenesis begins at tumor size 1-2 mm (10⁵ cells)
• Metastatic sites in order of frequency:
  1. Bone (most common): lumbar vertebrae > neck of femur > thoracic vertebrae > ribs > skull
  2. Lung/pleura
  3. Liver
  4. Brain
  5. Adrenal glands, ovaries (occasional)
• Bone mets: mostly osteolytic; occasionally osteosclerotic or mixed
• Bone marrow replacement → leukoerythroblastic anemia
• ILC specifically metastasizes to: peritoneum, GI, ovaries, leptomeninges

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9. CLINICAL FEATURES

Symptoms

• Hard, painless lump (most common presentation) - usually upper outer quadrant (50%)
• Skin changes: dimpling, peau d'orange, erythema, ulceration
• Nipple changes: retraction, discharge (bloody = most suspicious), Paget's changes
• Axillary lymphadenopathy

Signs on Examination

Quadrant distribution of breast cancers:

• Upper outer: 50%
• Upper inner: 15%
• Lower outer: 10%
• Lower inner: 5%
• Central/subareolar: 20%

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10. INVESTIGATIONS & IMAGING

Triple Assessment (Gold Standard)

1. Clinical examination
2. Imaging (mammography ± USG)
3. Tissue biopsy (FNAC or core needle biopsy)

Mammography

• Gold standard for screening (>40 years)
• Suspicious features:
  • Spiculated mass with irregular margins
  • Clustered microcalcifications (fine stippled, pleomorphic)
  • Asymmetric density
  • Architectural distortion
• Screening mammography reduces mortality by 20-33%
• BIRADS classification used to stratify findings (0-6)

Ultrasound

• Preferred in women <35 years (dense breasts)
• Distinguishes cystic vs. solid lesions
• Guides FNA/biopsy

MRI Breast

• Highest sensitivity (~90-95%) but lower specificity
• Indications: BRCA carriers, implants, occult primary, assessing extent, neoadjuvant response monitoring

Biopsy

• FNAC: cytology only; cannot distinguish invasive vs. in situ
• Core needle biopsy (CNB): histology; preferred - gives architecture, ER/PR/HER2 status
• Open excision biopsy: when CNB non-diagnostic

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11. TNM STAGING (AJCC 8th Edition)

T - Primary Tumor

N - Regional Lymph Nodes

M

Overall Stage Grouping

NEET SS note: The AJCC 8th edition introduced Prognostic Stage which adjusts anatomic stage based on ER/PR/HER2 and grade. TNBC is typically "up-staged"; Luminal A is "down-staged."

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12. SENTINEL LYMPH NODE BIOPSY (SLNB)

• Gold standard for axillary staging in clinically node-negative patients
• Sentinel node = first node to receive lymphatic drainage from the tumor
• Technique: Blue dye (Patent Blue V/Isosulfan blue) + Radioisotope (Tc-99m sulfur colloid) injected peritumorally
• Intraoperative assessment: frozen section or touch imprint cytology
• If sentinel node negative → no further axillary dissection needed
• If sentinel node positive → axillary lymph node dissection (ALND) OR completion axillary irradiation

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13. SURGICAL MANAGEMENT

Breast Surgery Options

BCS contraindications (absolute): multifocal/multicentric disease, previous breast irradiation, pregnancy (relative), positive margins after re-excision, inflammatory carcinoma, diffuse malignant microcalcifications

BCS + Radiation = Equivalent to MRM for survival (landmark NSABP B-06 trial)

Axillary Surgery

• SLNB → standard for cN0 (clinically node-negative)
• ALND (levels I & II) → cN1, failed SLNB, post-neoadjuvant with residual disease
• Z0011 trial: If 1-2 positive sentinel nodes + BCS + whole breast RT → no further ALND needed

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14. SYSTEMIC THERAPY

A. Chemotherapy

• AC-T: Doxorubicin (Adriamycin) + Cyclophosphamide × 4 → Paclitaxel (Taxol) × 4
• CMF: Cyclophosphamide + Methotrexate + 5-FU (older regimen)
• Anthracyclines + Taxanes: current backbone

1. Locally advanced breast cancer (T3, T4, N2, N3)
2. To downsize tumor for BCS
3. HER2-positive tumors
4. Triple-negative breast cancer
5. Premenopausal women with node-positive disease

• Pathologic Complete Response (pCR) after NACT = best prognostic marker; ~1/3 of TNBC and HER2+ achieve pCR

B. Endocrine Therapy (for ER/PR-positive tumors)

C. Targeted Therapy (HER2-positive)

D. PARP Inhibitors (BRCA-mutated)

• Olaparib, Talazoparib: for germline BRCA1/2-mutated HER2-negative (early or metastatic)
• Mechanism: synthetic lethality - block DNA repair in BRCA-deficient cells

E. CDK 4/6 Inhibitors (ER+/HER2- metastatic)

• Palbociclib, Ribociclib, Abemaciclib + aromatase inhibitor
• Standard of care for metastatic luminal breast cancer

F. Immunotherapy

• Pembrolizumab (anti-PD1): approved for high-risk early TNBC (with chemo) and PD-L1+ metastatic TNBC

G. Radiation Therapy

• Whole breast irradiation (WBI): mandatory after BCS
• Post-mastectomy RT (PMRT): ≥4 positive lymph nodes, T3/T4, positive margins
• Regional nodal irradiation: N2-N3 disease

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15. PROGNOSTIC FACTORS

Most Important (in order):

1. Axillary lymph node status - single most important prognostic factor in early breast cancer
2. Tumor size (T stage)
3. Histologic grade (Nottingham grade)
4. ER/PR/HER2 status (determines subtype)
5. Lymphovascular invasion (LVI)
6. Surgical margins
7. Age (<35 yrs = worse prognosis)

Biomarkers with NEET SS importance:

• ER+ → better prognosis (responds to hormone therapy); late recurrences (>10 years)
• HER2+ → aggressive but targetable; trastuzumab improves survival dramatically
• TNBC → worst short-term prognosis; chemo sensitive; recurrences within 5 years
• High TILs → better prognosis in TNBC and HER2+; better chemo response
• Ki-67 >20% = high proliferation index = aggressive tumor
• ESR1 mutations = endocrine therapy resistance (metastatic ER+ disease)

Gene Expression Assays:

• Oncotype DX (21-gene): ER+/HER2- early breast cancer; identifies who can avoid chemo
• MammaPrint (70-gene): similar utility; identifies high-risk vs. low-risk

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16. SPECIAL SITUATIONS

Male Breast Cancer

• Rare (~1% of all breast cancers)
• Usually presents late (more advanced stage)
• Almost always ER/PR positive
• BRCA2 mutation more common than BRCA1 (unlike female)
• Gynecomastia is NOT a risk factor
• Treatment: MRM (BCS rarely possible), hormone therapy (tamoxifen)

Bilateral Breast Cancer

• Synchronous (both at diagnosis) vs. metachronous (second primary after interval)
• ILC more likely to be bilateral than IDC

Locally Advanced Breast Cancer (LABC) - Stage III

• Definition: T3/T4 or N2/N3 disease
• Management: NACT first → surgery → adjuvant RT + systemic therapy

Metastatic (Stage IV) Breast Cancer

• Sites: Bone > Lung > Liver > Brain
• Goal: palliative (except in rare oligometastatic disease)
• Bone mets: bisphosphonates (zoledronic acid) or denosumab to reduce skeletal events
• Brain mets: stereotactic radiosurgery, whole brain RT, or systemic therapy

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17. SCREENING GUIDELINES (Key Points for NEET SS)

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18. HIGH-YIELD NEET SS MNEMONICS & QUICK FACTS

Must-Know One-Liners:

• Most common cancer in women globally: Breast cancer
• Most common histological type: IDC-NST (75%)
• Best prognosis histological type: Tubular carcinoma
• Worst prognosis: Inflammatory carcinoma (clinically); TNBC (molecularly)
• Bilateral marker (not precursor): LCIS
• E-cadherin negative: ILC and LCIS
• Paget cells: Large, pale, vacuolated cells in nipple epidermis; CEA+, CK7+
• Peau d'orange: dermal lymphatic blockage (NOT direct skin invasion by tumor)
• Skin dimpling: Cooper's ligament shortening (desmoplastic reaction)
• Most common site of mets: Bone (lumbar vertebrae first)
• Most common bone met type: Osteolytic
• Sentinel node technique: Blue dye + Tc-99m
• BCS = MRM in survival: NSABP B-06 trial
• BRCA1 cancers: Usually TNBC, high-grade
• BRCA2 cancers: Usually ER+, lower-grade
• pCR after NACT: Best predictor of long-term outcome in TNBC and HER2+
• HER2 targeted therapy: Trastuzumab (do NOT use with anthracyclines simultaneously - cardiotoxicity)
• Tamoxifen side effects: Endometrial cancer, DVT/PE, hot flashes
• Aromatase inhibitors side effects: Osteoporosis, arthralgia (no endometrial cancer)

MNEMONIC for Risk Factors - "BEACH FARM":

• BREAST feeding (protective)
• Early menarche
• Age / Alcohol
• Chemical exposure / Combined HRT
• History (family) / HER2
• Family history / BRCA
• Age at first birth (late)
• Radiation
• Menopause (late)

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19. QUICK COMPARISON TABLE (Exam-Focused)

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