Lesions of the Breast in Children and Adolescents

1. Normal Breast Development: Context

2. Non-Neoplastic / Developmental Abnormalities

Premature Thelarche

Gynecomastia

Accessory / Ectopic Breast Tissue (Polymastia / Polythelia)

3. Benign Breast Lesions

Fibroadenoma (Most Common)

• Pericanalicular fibroadenoma - fibrous tissue surrounding small tubular glands; smaller and harder; predominates in young women.
• Intracanalicular fibroadenoma - glands stretched into elongated spidery shapes, indented by fibrous tissue; softer and larger; more common in middle-aged women. Both represent a benign proliferation of epithelial and stromal components arising from a single lobule. - S. Das Manual on Clinical Surgery, p. 434

• Painless, slow-growing lump
• Smooth, firm, well-defined margins
• Not fixed to skin or deep structures
• Highly mobile - classically called a "breast mouse" or "floating tumour"
• No axillary lymphadenopathy
• Usually 1-3 cm at presentation; may rarely grow larger

• A clinically typical fibroadenoma confirmed on ultrasound in a patient under 25 years can be observed without biopsy.
• Biopsy is indicated if: age >25, atypical imaging features, rapid growth.
• Indications for surgical excision: age >30, suspicious features, atypia on histology, size >5 cm, family history of breast cancer, or patient preference.
• In children and adolescents, the preferred approach is conservative observation with ultrasound every 6-12 months. - Frontiers in Pediatrics, PMID 39507494

Solitary Breast Cyst

Galactocele

Breast Abscess / Mastitis

Duct Papilloma

4. Fibroepithelial Lesions

Phyllodes Tumor (Cystosarcoma Phyllodes)

• Smooth, multinodular, well-demarcated, firm, mobile and painless mass
• Average size 4-7 cm; can be massive
• Overlying skin may be stretched and tense; subcutaneous veins become prominent
• Skin ulceration may occur from pressure necrosis in very large tumors (not true invasion)
• Rarely infiltrates skin until late; remains mobile on the chest wall
• Palpable axillary nodes in up to 20% but true lymph node involvement is rare

Breast asymmetry resulting from a benign phyllodes tumor - Mulholland & Greenfield

• All grades: surgical excision to negative histological margins
• Breast-conserving surgery is appropriate even for large tumors
• SLNB is not routinely performed
• Adjuvant radiotherapy/chemotherapy: controversial; may be considered for large borderline or malignant tumors
• Post-treatment follow-up: chest X-ray every 6 months for 2 years, then annually for malignant phyllodes
• Systemic therapy for metastatic disease follows sarcoma protocols
• Mulholland & Greenfield, p. 3977; Berek & Novak, p. 985

5. Malignant Breast Lesions

Primary Breast Carcinoma

• Rare before age 18; incidence increases after puberty
• Secretory (juvenile) carcinoma is the most common type in children - a low-grade carcinoma with relatively favorable prognosis
• Other types: infiltrating ductal carcinoma (rare), adenocarcinoma
• Risk factors in pediatric patients include: prior thoracic radiation (e.g., for lymphoma), hereditary syndromes (BRCA1/2, Li-Fraumeni syndrome, Cowden syndrome/PTEN hamartoma)

Secondary / Metastatic Involvement

Breast Implant-Associated Anaplastic Large Cell Lymphoma (BIA-ALCL)

6. Diagnostic Approach

• Core needle biopsy (CNB) is the standard for tissue diagnosis when needed.
• Excisional biopsy is preferred over CNB in children when feasible, to minimize sampling error and to preserve breast architecture.
• Fine needle aspiration cytology (FNAC) is less preferred due to limited tissue.

7. Key Principles of Management in Children and Adolescents

1. Conservative approach first: Most lesions in this age group are benign and can be managed with watchful waiting and serial ultrasound.
2. Protect the breast bud: Never inadvertently excise the breast bud when draining an abscess or removing a periareolar mass in a prepubertal girl.
3. Multidisciplinary team: Malignant lesions require pediatric oncology, surgery, radiation oncology, and pathology input.
4. Patient and family counseling: Education about breast self-examination and when to seek attention for new or changing masses.
5. Imaging choice: Ultrasound first; avoid mammography in this population unless malignancy is strongly suspected.
6. Surgical conservatism: When excision is necessary, aim for enucleation or local excision with minimal tissue sacrifice to preserve cosmesis and lactation potential.

Summary Table

• A 2024 scoping review (Sosnowska-Sienkiewicz et al., Frontiers in Pediatrics, PMID 39507494) confirmed fibroadenomas account for ~95% of all pediatric breast lesions, advocated conservative management with ultrasound surveillance every 6-12 months for most cases, and emphasized that excisional biopsy should be reserved for complex or suspicious clinical/imaging scenarios.
• The 2025 APSA Cancer Committee expert consensus (Schwartz et al., J Pediatr Surg, PMID 39384492) provides an algorithm for pediatric surgeons emphasizing ultrasound-first evaluation, tissue preservation, and multidisciplinary management of the rare malignant lesion.

Papillary Lesions of the Breast

Classification Overview

1. Intraductal Papilloma (Benign)

Definition

Epidemiology and Types

• Most common type; arises in the large lactiferous ducts near the nipple
• Occurs predominantly in women 30-50 years of age
• The most common cause of bloody/serous nipple discharge
• Generally not associated with increased cancer risk
• Presents as a small soft mass just deep or lateral to the areola

• Arise in the terminal duct lobular unit (TDLU), peripheral to the nipple
• More likely to be bilateral
• Associated with a modestly increased risk of breast cancer (relative risk ~1.5-2x) compared to central papillomas
• May harbor atypical epithelial hyperplasia within them

Clinical Features

• Nipple discharge is the hallmark: spontaneous, unilateral, from a single ductal orifice
• Discharge character: serous, serosanguineous, or frankly bloody (bright red)
• A trigger point (localized pressure point) may be identified on the breast
• Occult blood test on the discharge is often positive
• A small, soft, cystic mass may be palpable just beneath/lateral to the areola
• Axillary lymphadenopathy is absent (unless malignant transformation has occurred)
• Considered pre-malignant if features of atypia are present - S. Das Manual on Clinical Surgery, p. 434

Important: Distinguishing Pathologic from Physiologic Discharge

• Spontaneous (not elicited)
• Unilateral and from a single duct orifice
• Bloody, serous, or serosanguineous
• Associated with a mass

Investigations

• Mammography and ultrasound are first-line imaging
• Breast MRI with contrast has largely replaced ductography as the investigation of choice for pathologic nipple discharge
• Ductography (galactography): contrast instilled into the involved duct; shows filling defect, ductal irregularity, or complete obstruction - valuable when MRI is unavailable
• Ductoscopy: fiberoptic scope placed into the duct for direct visualization; allows more precise excision localization
• Core needle biopsy: when a lesion is identified on imaging; however, excision is still recommended even after benign CNB result

Histopathology

• True fibrovascular cores lined by two cell layers: inner luminal epithelial cells and outer myoepithelial cells
• Myoepithelial cells are retained (key distinction from malignant papillary lesions)
• IHC: positive for myoepithelial markers (p63, calponin, smooth muscle actin, CK5/6) along the stalk and at the periphery

Management

• When a papilloma is diagnosed on core biopsy, surgical excision is the standard recommendation, as it may be associated with atypia or DCIS in the adjacent tissue
• Surgical technique:
  • Pressure applied around nipple to identify the discharging duct
  • Lacrimal duct probe placed into the affected duct
  • Duct excised via a periareolar incision (microdochectomy)
  • If single duct cannot be identified, a central duct excision (Hadfield's operation) is performed
  • Methylene blue dye can be injected after ductography to stain the duct for easier localization
  • Women of reproductive age should be counseled about potential difficulty breastfeeding following central duct excision - Mulholland & Greenfield's Surgery; Current Surgical Therapy 14e

2. Papilloma with Atypical Ductal Hyperplasia (ADH)

3. Papillary DCIS and Micropapillary DCIS (In Situ)

Papillary DCIS

• Ductal carcinoma in situ growing in a true papillary pattern: papillae with fibrovascular cores
• Key distinction from benign papilloma: the papillae in papillary DCIS lack a myoepithelial cell layer - this is the most important diagnostic feature
• The cells lining the papillae are monotonous, cytologically atypical, and there is no admixed myoepithelial cell population
• Often ER-positive, HER2-negative (low-grade pathway)
• May present as nipple discharge or be detected incidentally on imaging

Micropapillary DCIS

• A distinct architectural subtype of DCIS characterized by bulbous, club-shaped projections without fibrovascular cores (pseudo-papillae)
• The projections have no true fibrovascular stalk - this distinguishes it from true papillary DCIS
• More commonly multicentric and tends to involve larger areas of breast tissue, making margin assessment more difficult
• Can present as nipple discharge

Fig. 23.12 - DCIS patterns. (A-B) High-grade DCIS with comedo necrosis. (C) Cribriform DCIS. (D) Micropapillary DCIS - note bulbous projections without fibrovascular cores - Robbins Pathology

4. Encapsulated Papillary Carcinoma (EPC)

Morphology

• A papillary carcinoma enclosed within a fibrous capsule, without invasion of surrounding breast parenchyma
• The papillae are lined by low-grade atypical epithelial cells lacking myoepithelial cells (both on the stalks and at the periphery of the lesion)
• Absence of myoepithelial cells throughout is demonstrated by IHC (negative for p63, CK5/6, smooth muscle actin)

Controversy: In Situ or Invasive?

• One of the most debated areas in breast pathology (see [Rakha & Quinn, Histopathology 2025, PMID 39209705])
• Morphologically resembles in situ carcinoma (contained within capsule), but the absence of myoepithelial cells suggests it may represent an extremely low-grade form of invasive carcinoma
• Current WHO classification treats EPC as in situ unless there is clear invasion of surrounding stroma
• Prognosis is excellent regardless of designation

Clinical Features

• Typically presents as a palpable mass, sometimes with nipple discharge
• More common in older, postmenopausal women
• On imaging: well-circumscribed, cystic-solid mass; can be quite large

Management

• Surgical excision with clear margins
• Sentinel lymph node biopsy is generally not required for pure EPC
• Adjuvant therapy follows the usual guidelines for DCIS/early breast cancer (usually endocrine therapy given ER positivity)

5. Solid Papillary Carcinoma (SPC)

• A variant where the papillary fronds are so tightly packed that the lesion appears solid on low-power microscopy
• Often shows neuroendocrine differentiation (synaptophysin, chromogranin positive)
• Lacks myoepithelial cells
• May produce mucin (overlap with mucinous carcinoma)
• Like EPC, the in situ vs. invasive distinction is debated
• Often ER-positive, with a generally favorable prognosis
• Can be confused with invasive lobular carcinoma on biopsy - Hoda & Wen, Human Pathology 2025, PMID 40118257

6. Invasive Papillary Carcinoma

Epidemiology

• A special histological type of invasive breast carcinoma accounting for 2% of all invasive breast cancers
• Presents characteristically in the seventh decade of life
• Occurs disproportionately in non-white women

Morphology

• Defined by true papillary fronds with fibrovascular cores lined by multilayered atypical epithelium infiltrating beyond the duct walls into breast stroma
• Papillae are lined by malignant cells without myoepithelial cells
• Usually small tumors, rarely attaining >3 cm
• Typically ER-positive: ~87% express estrogen receptor (SEER data)

Behavior

• Low frequency of axillary lymph node metastases - one of the most favorable special types
• 5- and 10-year survival rates are similar to mucinous carcinoma and tubular carcinoma (both excellent prognoses among special-type cancers) - Schwartz's Principles of Surgery, p. 593

Management

• Breast-conserving surgery or mastectomy depending on tumor size and patient preference
• Axillary staging (SLNB) recommended
• Adjuvant endocrine therapy for ER-positive tumors

7. Invasive Micropapillary Carcinoma

Morphology

• Tumor cells form hollow balls ("morulae") that appear to float within intercellular fluid-filled spaces, mimicking papillae but without fibrovascular cores
• The cells show reversed polarity (apical surfaces face outward, toward the stroma - the "inside-out" pattern)
• This reversed polarity is demonstrated by EMA (epithelial membrane antigen) staining on the outside of the cell clusters

Clinical Behavior

• More aggressive than ordinary invasive carcinoma of no special type
• High rate of lymphovascular invasion and lymph node metastases
• Tends to overexpress HER2
• Management follows standard protocols for invasive carcinoma but with attention to aggressive locoregional management

8. Paget's Disease of the Nipple (Papillary/Ductal Extension)

• Presents as a chronic eczematous, erythematous, scaling eruption of the nipple with pruritus
• Pathognomonic: large, pale, vacuolated Paget cells in the rete pegs of the epidermis
• Paget cells are identical to the underlying DCIS cells (pagetoid change)
• ~50% of patients have a palpable mass (usually associated with invasive carcinoma)
• Without a palpable mass, underlying DCIS is the rule
• IHC distinction: CK7+ and CEA+ (Paget's) vs. S-100+ (melanoma - which it can mimic)

Paget disease: DCIS extends up lactiferous ducts into nipple skin, disrupting the epithelial barrier and causing a weeping scaly crust - Robbins Pathology

Key Diagnostic Distinguishing Features

The "B3" Problem: Papilloma on Core Needle Biopsy

• Sampling error on CNB may miss associated atypia or DCIS
• Even a benign-appearing papilloma on CNB may harbor atypia at surgical excision
• The 2024 EUSOMA/EUSOBI/ESP guidelines (Rubio et al., PMID 38061151) recommend surgical excision for most papillary lesions on CNB, with observation acceptable only for small (<1 cm), incidentally found peripheral papillomas without atypia, after multidisciplinary discussion

Summary of Management

• A 2025 pathology review (Hoda & Wen, Human Pathology, PMID 40118257) highlights persistent challenges in diagnosing SPC and EPC on CNB, noting overlap with invasive lobular carcinoma as a major pitfall, and stresses that a "fibroepithelial lesion" or papillary pattern on CNB always warrants excision.
• Rakha & Quinn, Histopathology 2025, PMID 39209705 provides a framework for EPC categorization and addresses the unresolved in situ vs. invasive debate, recommending that pathologists apply IHC for myoepithelial markers systematically and recognize morphologic overlap with high-grade circumscribed invasive carcinomas.

Prognostic Markers in Breast Carcinoma

Classification of Prognostic Markers

1. Clinicopathological markers - tumor size, lymph node status, histological grade, histological type, lymphovascular invasion
2. Biomarker/IHC markers - hormone receptors (ER, PR), HER2, Ki67, p53
3. Molecular/genomic markers - gene expression profiling (Oncotype DX, MammaPrint, PAM50), molecular subtypes

I. Clinicopathological Prognostic Markers

1. Axillary Lymph Node Status

• Node-negative disease: 10-year survival ~70-80%
• 1-3 positive nodes (pN1): significantly worse prognosis
• 4-9 positive nodes (pN2): markedly worse
• ≥10 positive nodes (pN3): poorest prognosis in this category

2. Tumor Size (T Stage)

3. Histological Grade (Nottingham Grading System)

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

4. Histological Type / Special Type

5. Lymphovascular Invasion (LVI)

• Predicts lymph node positivity even when nodes appear negative
• Associated with higher risk of systemic recurrence
• Particularly significant in node-negative patients (upstages risk)
• Strong indicator for adjuvant chemotherapy in otherwise low-risk cases

6. Margins of Excision

II. Biomarker / Immunohistochemical Prognostic Markers

1. Estrogen Receptor (ER) and Progesterone Receptor (PR)

• ER/PR positivity predicts a more favorable long-term prognosis (though early outcome may be similar)
• Patients with hormone receptor-positive tumors survive 2-3 times longer after a diagnosis of metastatic disease than patients with hormone receptor-negative tumors
• ER/PR-negative status is associated with higher grade, higher Ki67, earlier relapse, and worse 5-year survival

• ER positivity predicts benefit from endocrine therapy (tamoxifen, aromatase inhibitors)
• PR positivity confirms a functional ER pathway
• ER-/PR+ is rare; ER+/PR- has intermediate hormonal sensitivity
• Tumors negative for both ER and PR are not candidates for endocrine therapy

2. HER2 (Human Epidermal Growth Factor Receptor 2 / ErbB2)

• IHC (protein overexpression): scored 0, 1+, 2+, 3+
  • 0 or 1+ = negative
  • 2+ = equivocal → reflex FISH/ISH testing
  • 3+ = positive (>10% complete, intense membrane staining)
• FISH/CISH (gene amplification): ratio of HER2 gene signals to chromosome 17 centromere signals ≥2.0 = amplified

• HER2 overexpression/amplification is associated with:
  • Poorly differentiated tumors with high proliferation rates
  • Higher incidence of positive lymph nodes
  • Decreased hormone receptor expression
  • Increased risk of recurrence and death
  • More aggressive clinical behavior
• Before anti-HER2 therapy: HER2+ was one of the worst prognostic subtypes
• With trastuzumab + pertuzumab: outcomes have dramatically improved (40-50% reduction in recurrence risk)

3. Ki67 (Proliferation Index)

• Measured by: IHC, expressed as percentage of positively staining tumor cells
• Thresholds:
  • Low: <15-20%
  • High: >20-30% (cut-offs vary by institution; international consensus seeks standardization)

• High Ki67 correlates with:
  • High histological grade
  • ER negativity
  • p53 overexpression
  • Aneuploidy and high S-phase fraction
  • Lymph node metastases
  • Worse disease-free and overall survival
• Ki67 forms part of the IHC4 panel (ER, PR, HER2, Ki67) that provides prognostic information comparable to the 21-gene Oncotype DX recurrence score, at lower cost - though reproducibility across labs remains a limitation
• Ki67 is key in distinguishing Luminal A (Ki67 <20%) from Luminal B (Ki67 ≥20%) subtypes - Schwartz's Principles of Surgery, p. 606

4. p53 / TP53

• p53 overexpression (by IHC) reflects mutant p53 accumulation due to loss of normal ubiquitin-mediated degradation
• Mutant TP53 is found in ~20-30% of breast cancers overall; ~80% of TNBC
• Associated with: high grade, ER negativity, lymph node metastases, high Ki67, high S-phase fraction, and reduced overall survival
• p53 overexpression predicts worse outcome, particularly in node-negative disease
• An angiogenesis index combining microvessel density (CD31), thrombospondin, and p53 has been developed as a composite prognostic tool

5. bcl-2 and Apoptosis Markers

• bcl-2 (anti-apoptotic protein): paradoxically, bcl-2 expression in breast cancer is associated with ER positivity and better prognosis (inverse to its oncogenic role in lymphoma)
• bax (pro-apoptotic): decreased bax expression correlates with lymph node metastases, poor chemotherapy response, and decreased overall survival
• The bax:bcl-2 ratio influences whether cells undergo apoptosis; overexpression of bcl-2 and a decreased bax:bcl-2 ratio correlate with high grade, lymph node positivity, and reduced survival
• Schwartz's Principles of Surgery, p. 691

6. Angiogenesis Markers (VEGF / Microvessel Density)

• VEGF (vascular endothelial growth factor) overexpression in invasive breast cancer correlates with increased microvessel density and recurrence, particularly in node-negative disease
• A combined angiogenesis index (microvessel density by CD31 + thrombospondin + p53) has prognostic value
• Currently used primarily in research; bevacizumab (anti-VEGF) did not produce durable clinical benefit in trials and is no longer routinely used in breast cancer

7. EGFR (Epidermal Growth Factor Receptor / HER1)

• EGFR overexpression correlates with:
  • ER-negative status
  • p53 overexpression
  • Higher grade
  • Worse prognosis
• EGFR expression is a hallmark of basal-like/TNBC (basal cytokeratins CK5/6 + EGFR positivity defines a subgroup with particularly poor outcomes)

III. Molecular Subtypes (Gene Expression Profiling)

Fig. 23.15 - Breast cancer classification by morphology, biomarkers, and gene expression profiling - Robbins Pathology

Fig. 68.10 - Heat map of global gene expression in breast cancer showing clustering into luminal (blue), HER2+ (green), and basal-like/TNBC (red) subtypes - Sabiston Textbook of Surgery

Luminal A (35-45% of breast cancers)

• IHC profile: ER+, PR+ (high), HER2-, Ki67 low (<20%)
• Molecular features: High ER/luminal gene expression; 1q gain, 16q loss
• Behavior: Low grade (typically Grade 1-2), slow proliferation, excellent prognosis
• Treatment: Endocrine therapy alone usually sufficient; chemotherapy often avoidable
• 10-year survival: Approximately 80-90%

Luminal B (20-25% of breast cancers)

• IHC profile: ER+ (lower levels), PR-, HER2- or HER2+, Ki67 high (≥20%)
• Molecular features: Higher genomic instability than Luminal A
• Behavior: Higher grade (typically Grade 2-3), greater proliferation, higher risk of recurrence
• Treatment: Endocrine therapy + chemotherapy (anthracycline/taxane-based)
• Prognosis: Intermediate; worse than Luminal A

HER2-Enriched (5-10% of breast cancers)

• IHC profile: HER2 overexpression/amplification; may be ER+/-
• Molecular features: HER2 amplicon overexpression; often TP53 mutation
• Behavior: High grade, high proliferation, historically aggressive
• Treatment: Anti-HER2 therapy (trastuzumab + pertuzumab) + chemotherapy; outcomes markedly improved with targeted therapy
• Prognosis: Poor without anti-HER2 therapy; much improved with it

Basal-Like / Triple Negative Breast Cancer (TNBC) (15-20%)

• IHC profile: ER-, PR-, HER2- (triple negative); often expresses basal markers CK5/6, EGFR
• Molecular features: High frequency of TP53 mutations; BRCA1 dysfunction common (80% of BRCA1-mutated cancers are basal-like)
• Behavior: High grade (usually Grade 3), very high Ki67, early visceral metastases (lung, brain - not bone/liver as often seen in luminal types)
• Treatment: Chemotherapy (no targeted therapy until recently); pembrolizumab (PD-L1+), olaparib (BRCA mutated), sacituzumab govitecan
• Prognosis: Worst overall survival; paradoxically, higher complete response rates to neoadjuvant chemotherapy; poor prognosis if residual disease after neoadjuvant therapy
• Sabiston Textbook of Surgery, p. 1390

Note: The clinical IHC classification does not exactly overlap with gene expression profiling. Approximately 20% of IHC-defined TNBC are NOT basal-like by molecular profiling, and some HER2+ tumors are luminal by profiling.

IV. Genomic / Multigene Assays

1. Oncotype DX (21-Gene Recurrence Score) - Most Widely Used

• Technology: RT-PCR on FFPE paraffin-embedded tumor tissue
• Genes: 16 cancer-related genes + 5 reference genes
• Output: Recurrence Score (RS) 1-100

• Evidence: TAILORx trial validated that women with RS 0-25 (age >50) and RS 0-15 (age <50) derive no benefit from adding chemotherapy to endocrine therapy
• Predicts both recurrence risk AND benefit from chemotherapy in ER+/HER2-/N0 and N1 (1-3 nodes) disease
• Ki67 included in the gene panel; the four-marker IHC4 panel (ER, PR, HER2, Ki67) provides similar information at lower cost - Bailey & Love's Surgery, p. 962; Sabiston Textbook of Surgery, p. 1390

2. MammaPrint (70-Gene Recurrence Assay)

• Technology: Microarray analysis of 70 genes; can use fresh/frozen or FFPE tissue
• Output: Binary readout - low risk or high risk
• Applicable to both ER+ and ER- tumors; Node-negative AND limited node-positive disease
• Evidence: MINDACT trial showed ~46% of clinically high-risk patients were genomically low risk and could safely avoid chemotherapy
• Validated in premenopausal and postmenopausal women - Bailey & Love's Surgery, p. 962

3. PAM50 / Prosigna

• Identifies the four molecular subtypes (Luminal A, Luminal B, HER2-enriched, Basal-like) using 50-gene expression analysis
• Provides a Risk of Recurrence (ROR) score
• Particularly useful for determining late distant recurrence risk (years 5-10) in ER+ patients on endocrine therapy

4. EndoPredict and Breast Cancer Index (BCI)

• Both provide prognostic information for late recurrence risk in ER+/HER2- early breast cancer
• BCI uniquely predicts benefit from extended endocrine therapy (beyond 5 years)

V. Genetic / Germline Markers

BRCA1 and BRCA2

• BRCA1 mutations confer susceptibility to breast AND ovarian cancer; ~45% of hereditary breast cancers carry BRCA1 germline mutations
• BRCA2 mutations also increase breast cancer risk; associated with male breast cancer, ovarian, pancreatic, and prostate cancers
• BRCA1-associated breast cancers: typically triple negative, high grade, basal-like subtype
• BRCA2-associated breast cancers: more commonly ER+ luminal type
• Germline BRCA1/2 mutation carriers: ~10% of women with breast cancer diagnosed at ≤40 years
• Therapeutic implications: PARP inhibitors (olaparib, talazoparib) have demonstrated survival benefit in BRCA-mutated HER2-negative metastatic breast cancer - making this both a prognostic AND predictive marker
• Other hereditary syndromes: TP53 (Li-Fraumeni), PTEN (Cowden), CDH1, PALB2, ATM, CHEK2

VI. Pathological Complete Response (pCR) after Neoadjuvant Therapy

• pCR predicts superior event-free and overall survival
• Most predictive in TNBC and HER2-enriched subtypes
• Luminal A tumors rarely achieve pCR (low chemosensitivity), but have good outcomes regardless
• Residual disease after neoadjuvant therapy in TNBC is an indication for adjuvant capecitabine (CREATE-X trial)

Summary: Integrated Prognostic Assessment

• Oncotype DX (RS <18): Safely omit chemotherapy in ER+/HER2-/N0-N1 disease
• MammaPrint (low risk): Safely omit chemotherapy in genomically low-risk patients regardless of clinical risk

• The 2024 molecular classification review (Roy et al., PET Clinics, PMID 37268505) consolidates the correlation between IHC subtypes and molecular subtypes, and highlights emerging PET-based molecular characterization of breast tumors.
• Kang & Kim, Cancer Research and Treatment 2024 (PMID 38291745) defines HER2-low (IHC 1+ or 2+/ISH-) as a newly actionable prognostic/predictive category, constituting ~55-60% of all breast cancers, now targetable with trastuzumab deruxtecan (T-DXd).
• Dvir et al., Int J Mol Sci 2024 (PMID 39062758) updates immunotherapy biomarkers: PD-L1 CPS ≥10 (by VENTANA SP142 assay) predicts pembrolizumab benefit in early TNBC and metastatic TNBC.

Premalignant Lesions of Skin

1. Actinic (Solar) Keratosis (AK)

• Appear after age 50; more common in men
• Fitzpatrick skin types I-III (fair skin, tendency to burn) at highest risk
• 40-50% of Australians over 40 years affected; 11-25% in the US
• Prevalent on face, scalp, dorsal hands, neck (>80% of lesions)

• Usually asymptomatic; noticed due to rough texture
• Dry, erythematous, scaly lesions on sun-exposed skin
• Thin lesions more easily palpable than visible
• Covered with an adherent scale; may be pigmented or telangiectatic
• Thick lesions may have marked hyperkeratosis forming a cutaneous horn
• Surrounding skin shows solar elastosis (thickened, yellow, wrinkled skin)

• Thin/small lesions: moisturizer, keratolytic (salicylic acid); spontaneous resolution in 21%
• Cryotherapy (liquid nitrogen): effective for thicker lesions; painful, may scar
• 5-Fluorouracil (5-FU) cream: once/twice daily for 6 weeks; excellent cosmetic result
• Imiquimod cream: immune response modifier; 3x/week for 4 weeks
• Ingenol mebutate: 2 daily applications for head/neck AKs
• Photodynamic therapy (PDT) with methyl aminolevulinic acid + red light: highly effective, good cosmesis
• Surgery (curettage or excision): when other treatments fail or diagnostic doubt
• Prevention: sunscreen is the only intervention that reduces AK formation; photoprotection counseling is mandatory - Scott-Brown's Otorhinolaryngology, p. 1365-1366

2. Bowen's Disease (BD) - Squamous Cell Carcinoma In Situ

• Adults >60 years; slightly more common in women (UK data); men more commonly on scalp and trunk
• Head and neck, lower limbs (in UK, 67% on lower limbs)
• Usually solitary; multiple in ~20% of cases

• Chronic UV radiation (most common)
• Arsenic exposure
• Immunosuppression
• HPV infection (mucosal BD)
• Ionizing radiation, PUVA therapy

• Long-standing, slowly growing, usually asymptomatic lesion
• Well-defined, sharply demarcated, scaly erythematous plaque on sun-exposed skin
• Surface: scaling, crusting, or hyperkeratotic
• Usually pink/red; may be gray or brownish; rarely pigmented
• Flat plaque may eventually become nodular or verrucous (suggests invasive SCC)

Bowen's disease - scaly erythematous plaque with hyperkeratotic surface - Fitzpatrick's Dermatology

Histology of Bowen's disease - full-thickness epidermal dysplasia with abnormal mitoses above an intact basement membrane - Fitzpatrick's Dermatology

• Disordered architecture
• Abnormal mitoses, nuclear hyperchromasia and pleomorphism
• Hyperkeratosis
• Dysplastic cells extending along hair follicle epithelium (but NOT invading basement membrane)

• 5-Fluorouracil cream: highly effective for most lesions
• Imiquimod: particularly useful for HPV-associated BD
• Cryotherapy: effective; limited by pain and slow healing in large lesions
• PDT: cure rates ~90%; preferred for large or difficult sites
• Curettage and cautery: simple, effective; allows histology but cannot always exclude invasion
• Surgical excision with 2 mm margin: for clinically suspicious lesions or when conservative treatment fails; Mohs surgery for difficult sites
• Skin biopsy is recommended to confirm diagnosis before treatment - Scott-Brown's p. 1366-1367; Fitzpatrick's Dermatology

3. Keratoacanthoma (KA)

• Rapidly growing crateriform nodule with a central keratin plug, usually on sun-exposed skin
• Considered by many a well-differentiated SCC variant (low-grade SCC)
• Characteristically enlarges rapidly over weeks then may spontaneously involute
• Features suspicion of malignancy: size >2 cm, failure to involute, perineural invasion on histology
• Management: Surgical excision (preferred); allows histological confirmation and excludes invasive SCC - Goldman-Cecil Medicine

4. Dysplastic (Atypical) Melanocytic Nevi

• Melanocytic nevi with atypical clinical and histological features
• Dysplastic nevi exist in 2-8% of the general population
• Development of >5 atypical melanocytic nevi carries a 5-fold increase in melanoma risk
• Development of >100 acquired melanocytic nevi = 10-fold increase in melanoma risk
• Dysplastic nevus syndrome (DNS) / Familial Atypical Multiple Mole Melanoma (FAMMM): autosomal dominant; markedly elevated lifetime risk of melanoma

5. Congenital Melanocytic Nevi (CMN)

• Present at birth or appear in infancy
• Giant CMN (>20 cm) carries the highest risk of melanoma transformation (~5-12% lifetime risk)
• Small/medium CMN: very low malignant risk
• Management: prophylactic excision considered for giant CMN; surveillance for smaller lesions

6. Solar (Actinic) Lentigo

• Flat, well-circumscribed, tan-brown macules on chronically sun-exposed skin (face, dorsal hands)
• Also called "liver spots" or "age spots"
• Groups of solar lentigines carry a 4-fold increase in melanoma risk
• Lentigo maligna (Hutchinson's melanotic freckle) is a special form that represents melanoma in situ on chronically sun-damaged skin and can progress to lentigo maligna melanoma

7. Leukoplakia

• White patch or plaque on a mucous membrane (oral cavity, vulva, glans penis) that cannot be scraped off and cannot be classified as any other definable lesion
• Histologically shows a range from hyperkeratosis → mild dysplasia → severe dysplasia → carcinoma in situ
• Malignant transformation rate: ~5% over 10 years for oral leukoplakia
• Erythroplakia (red velvety patch): higher malignant potential than leukoplakia; ~40-50% contain carcinoma at time of biopsy
• Speckled leukoplakia (mixed red and white): intermediate risk
• Management: biopsy to establish grade of dysplasia; excision or ablation for high-grade dysplasia; cessation of tobacco/alcohol

8. Chronic Scars, Ulcers, and Sinuses (Marjolin's Ulcer)

• Malignant transformation can occur in chronic non-healing wounds, burn scars, osteomyelitis sinuses, and post-irradiation scars
• The resulting tumor is usually a well-differentiated but aggressive SCC - Marjolin's ulcer
• Long latent period (typically 20-40 years after original injury)
• Diagnosis often delayed due to being hidden in existing wound
• More aggressive than de novo SCC: higher rate of lymph node metastasis despite well-differentiated histology
• Management: wide excision; regional node assessment

9. Radiation Dermatitis (Radiodermatitis)

• Chronic radiation damage following therapeutic or occupational ionizing radiation exposure
• Presents as atrophic, telangiectatic, dyspigmented skin with loss of adnexal structures
• Progresses to SCC after a latency of years to decades
• Risk is also elevated for BCC in irradiated fields

Summary Table

• Most premalignant skin lesions are induced by ultraviolet light
• Photoprotection (sunscreen, avoidance of UV) is the only intervention proven to reduce AK formation
• Any premalignant lesion showing induration, ulceration, rapid growth, or bleeding warrants urgent biopsy to exclude invasive SCC
• Patients with precursor lesions must be educated to recognize early signs of skin cancer and seek early medical attention - Scott-Brown's Otorhinolaryngology, p. 1367