Invasive Carcinoma of the Breast

Slide 1 · Invasive Carcinoma

of the Breast

Morphology · Molecular phenotypes · Clinicopathologic integration

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Distinguish stromal invasion from in situ breast carcinoma.

Relate histologic type and grade to breast cancer biology.

Interpret ER, PR, HER2, stage and major prognostic variables.

Connect morphologic patterns with clinical presentation and diagnostic pitfalls.

Slide 3 · What defines invasive breast carcinoma?

Malignant epithelial cells extend beyond the basement membrane into breast stroma.

Invasion permits access to lymphovascular routes and distant dissemination.

Invasion status, histologic type, grade and anatomic extent are distinct diagnostic outputs.

Slide 4 · In situ disease versus stromal invasion

Schematic — not a histologic specimen

IN SITU

INVASIVE

Morphologic interpretation

In situ: Atypical epithelial cells remain enclosed by the myoepithelial–basement membrane interface.

Invasive: Malignant cells breach that boundary and enter surrounding stroma.

Slide 5 · Four complementary dimensions of a diagnosis

Invasion status

Histologic type

Histologic grade

Anatomic stage

Biomarkers and molecular alterations further refine prognosis and therapy selection.

Slide 6 · Pathology classification has two distinct axes

Morphologic axis

In situ versus invasive

No special type versus defined special histologic type

Nottingham grade and extent

Biologic axis

ER and PR nuclear expression

HER2 protein / gene status

Selective genomic or gene-expression assays

Slide 7 · Three major routine clinical groups

Luminal

ER-positive / HER2-negative

Usually endocrine-responsive

Variable grade and proliferation

HER2-positive

HER2 overexpression or amplification

Targetable ERBB2 pathway

ER may be positive or negative

Triple-negative

ER-negative / PR-negative / HER2-negative

Biologically heterogeneous

Often high-grade and proliferative

Slide 8 · Molecular subtyping is more granular

Expression profiling describes luminal A, luminal B, HER2-enriched, basal-like, normal-like and claudin-low groups.

These intrinsic classes correlate imperfectly with ER/HER2 clinical assays.

Expression signatures can add prognostic or predictive information in selected settings.

Slide 9 · Global burden context

Breast cancer became the most commonly diagnosed cancer worldwide in 2020.

The chapter reports approximately 2.3 million new cases worldwide in that year.

Earlier detection and more effective adjuvant treatment have improved outcomes, unequally across settings.

Slide 10 · Age is linked to subtype distribution

Breast cancer is uncommon before age 25 and incidence rises with age.

ER-positive luminal tumors continue to rise in incidence at older ages.

HER2-positive and triple-negative tumors contribute a larger fraction of cancers in younger patients.

Slide 11 · How invasive tumors first come to attention

Screen-detected

Often relatively small

Usually nonpalpable

More commonly luminal

Symptom-detected

Palpable irregular mass

May show skin or nipple change

More common with rapidly growing subtypes

Slide 12 · Detection and clinical correlation

Mammography can detect a density, architectural distortion or calcifications; None is cancer-specific.

Ultrasonography, tomosynthesis and MRI may clarify lesions occult on conventional views.

A negative screening image does not exclude an invasive tumor when clinical suspicion remains.

Slide 13 · Clinical manifestations of local invasion

Desmoplastic stromal growth can produce a hard, irregular breast mass.

Skin tethering causes dimpling; Central tumors may retract the nipple.

Advanced local spread can involve the dermis or chest wall.

Slide 14 · Breast carcinoma risk is multifactorial

Constitutional

Increasing age

Inherited susceptibility and family history

Prior breast carcinoma

Hormonal / exposure

Cumulative estrogen exposure

Reproductive history and exogenous hormones

Postmenopausal obesity and physical inactivity

Slide 15 · Estrogen exposure and luminal cancer

Estrogen stimulates epithelial proliferation and influences gene transcription.

Repeated cell cycling creates opportunities for the acquisition and fixation of mutations.

Estrogen signaling can also promote growth of an established ER-positive neoplastic clone.

Slide 16 · Two broad evolutionary pathways

Precursor alteration

In situ neoplasia

Stromal invasion

Invasive carcinoma

Low-grade and high-grade cancers often follow distinct evolutionary trajectories; They are not absolutely isolated.

Slide 17 · Low-grade versus high-grade routes

Low-grade neoplasia

Columnar cell lesion → atypia

Low-grade DCIS / classic LCIS

Typically luminal, ER-positive

High-grade neoplasia

Early precursor incompletely defined

High-grade DCIS

More genomic instability; Several clinical phenotypes

Slide 18 · Characteristic alterations in low-grade evolution

Gain of chromosome 1q and loss of 16q are characteristic genomic changes.

PIK3CA activation is encountered in the luminal pathway.

Many lesions remain indolent; Progression requires additional biologic events.

Slide 19 · Characteristic alterations in high-grade evolution

High-grade tumors more often show TP53 mutations and complex chromosomal changes.

HER2 amplification and DNA repair defects define biologically important subsets.

High-grade DCIS is a recognized precursor, but earlier steps are less clearly characterized.

Slide 20 · The invasive transition: Epithelial–stromal interface

Schematic — not a histologic specimen

IN SITU

INVASIVE

Morphologic interpretation

In situ precursors may contain many of the same driver alterations as invasive carcinomas.

Breakdown of the myoepithelial–basement membrane interface and microenvironmental changes may facilitate invasion.

Slide 21 · Tumor microenvironment is an active participant

Cancer-associated fibroblasts can remodel extracellular matrix and facilitate invasion.

Myoepithelial–stromal interactions contribute to basement membrane integrity.

Tumor and immune cell signaling can help establish an immunosuppressive microenvironment.

Slide 22 · Genetic predisposition: The two-hit principle

Inherited susceptibility allele

Acquired alteration of remaining allele

Loss of protective function

Clonal tumor evolution

This tumor-suppressor model is important for BRCA-associated breast cancer.

Slide 23 · BRCA1 and BRCA2: Repair pathway biology

BRCA1 and BRCA2 help maintain genomic integrity through homologous recombination repair.

Inactivation favors accumulation of DNA damage and genomic instability.

BRCA1-associated breast carcinomas are commonly triple-negative; BRCA2-associated cancers are often ER-positive.

Slide 24 · Selected susceptibility genes and associated patterns

BRCA1 / BRCA2

Homologous recombination repair

BRCA1: Often TNBC

BRCA2: Often luminal

TP53 / PTEN

Cell growth and genome control

Li–Fraumeni / Cowden syndromes

Distinct cancer spectra

CDH1 / PALB2

Adhesion / DNA repair

CDH1: Lobular type

PALB2: Luminal or TNBC

Slide 25 · Synthetic lethality in homologous recombination deficiency

BRCA-pathway defect

Impaired double-strand break repair

PARP-pathway inhibition

Accumulation of lethal DNA damage

A biologic rationale for PARP inhibitor sensitivity in selected hereditary-associated cancers.

Slide 26 · Luminal carcinoma: Defining biology

ER-positive / HER2-negative tumors represent the largest routine clinical group.

Estrogen-regulated transcription is central to their tumor biology.

They span low-grade, slowly proliferating tumors to more aggressive proliferative cancers.

Slide 27 · Luminal A–like phenotype

Strong ER-driven gene-expression program; Usually PR-positive.

Lower proliferation and better glandular differentiation are typical.

PIK3CA mutations, 1q gain and 16q loss are recurring associations.

Slide 28 · Luminal B–like phenotype

Stronger proliferation-associated expression than luminal A.

Often lower ER/PR protein levels and greater genomic complexity.

May be less differentiated and more clinically aggressive than luminal A.

Slide 29 · Luminal A versus luminal B: Conceptual distinction

Luminal A

Dominant estrogen-response signature

Low proliferation

Generally lower grade

Luminal B

Enhanced proliferation signature

Higher proliferation

Often higher grade

Slide 30 · HER2-positive carcinoma: Defining event

HER2 (ERBB2) is a receptor tyrosine kinase encoded on chromosome 17q.

HER2 amplification is the major cause of HER2 protein overexpression.

Downstream signaling includes pathways favoring proliferation and cell survival.

Slide 31 · HER2 signaling links genotype to phenotype

ERBB2 copy-number gain

HER2 receptor overexpression

Growth / survival signaling

Highly proliferative carcinoma

Pathway diagram is conceptual; Individual signaling steps are simplified.

Slide 32 · Two complementary ways to assess HER2

Immunohistochemistry

Protein overexpression at cell membrane

Assesses expression in tumor cells

Requires appropriate scoring and controls

In situ hybridization

HER2 gene copy-number changes

Assesses gene amplification

Interpreted with laboratory-validated criteria

Slide 33 · Triple-negative breast carcinoma is heterogeneous

Triple-negative is a clinical immunophenotype, not a single molecular entity.

Many tumors have a basal-like gene-expression signature.

High-grade cancers often show marked genomic instability and proliferative activity.

Slide 34 · Homologous recombination defects in TNBC

BRCA1/BRCA2 dysfunction and related repair deficiencies are biologically important.

Genomic copy-number alterations and rearrangements can be extensive.

The degree and mechanism of repair deficiency differ between individual tumors.

Slide 35 · Clinical phenotypes are not intrinsic subtypes

Routine surrogate classification

ER / PR immunohistochemistry

HER2 immunohistochemistry or ISH

Available in standard workflows

Intrinsic expression classes

Genome-wide expression patterns

More complex biological taxonomy

Not routinely required for all diagnoses

Slide 36 · Role of multigene expression assays

Selected mRNA signatures contribute prognostic information beyond basic morphology.

Many signatures emphasize proliferation-associated genes.

Clinical utility is context-dependent, particularly within certain ER-positive cancers.

Slide 37 · Invasive carcinoma of no special type (NST)

NST is the predominant morphologic category of invasive breast cancer.

It encompasses tumors without defining features of a special histologic type.

Architecture, cytologic atypia, immune infiltration and desmoplasia vary widely.

Slide 38 · NST: Irregular invasive nests in a stromal reaction

Schematic — not a histologic specimen

Morphologic interpretation

Irregular malignant epithelial glands and nests dissect into fibrous stroma.

A desmoplastic reaction can account for firmness and spiculated margins.

Slide 39 · Gross appearance of NST carcinoma

A firm, irregular mass with radiodense or spiculated margins is typical.

Cut surfaces may appear pale or chalky-white when desmoplasia is prominent.

Some cancers are deceptively circumscribed or diffuse with little stromal reaction.

Slide 40 · NST may not form a discrete mass

Scattered cells or tiny neoplastic glands may infiltrate otherwise normal fibrofatty tissue.

Some high-grade carcinomas grow as cellular sheets with relatively little desmoplasia.

Morphology and clinical imaging must be correlated rather than assumed concordant.

Slide 41 · Nottingham histologic grade is multidimensional

Tubule formation

Nuclear pleomorphism

Mitotic activity

Integrated histologic grade

Grade reflects differentiation and proliferation; It is not interchangeable with stage.

Slide 42 · Grade 1: Well differentiated

Schematic — not a histologic specimen

Morphologic interpretation

Predominantly gland-forming architecture with relatively uniform nuclei.

Low proliferative activity and infrequent mitoses.

Slide 43 · Grade 2: Intermediate differentiation

Schematic — not a histologic specimen

Morphologic interpretation

Mixture of glandular structures and solid or infiltrative groups.

Greater nuclear variation and mitotic activity than grade 1.

Slide 44 · Grade 3: Poorly differentiated

Schematic — not a histologic specimen

Morphologic interpretation

Ragged solid nests or sheets with little gland formation.

Marked nuclear pleomorphism, high proliferation and possible necrosis.

Slide 45 · Grade and stage answer different questions

Histologic grade

How differentiated and proliferative is the carcinoma?

Tubules, nuclei, mitoses

Biologic aggressiveness

Anatomic stage

How far has carcinoma spread?

Tumor extent, nodes, metastasis

Disease burden

Slide 46 · Morphologic spectrum of invasive carcinoma

Schematic — not a histologic specimen

Tubules

Mixed nests

Solid sheets

Morphologic interpretation

Invasive breast carcinomas range from well-formed infiltrative tubules to poorly differentiated cellular sheets.

The diagnostic category must integrate invasion, defining subtype features and grading.

Slide 47 · Why special histologic types matter

Defined architectural or cytologic patterns can correlate with distinct genomic alterations.

Some subtypes have characteristic biomarker profiles and clinical behavior.

Recognizing a special subtype can materially change differential diagnosis and prognostic interpretation.

Slide 48 · Invasive lobular carcinoma: The adhesion defect

Loss of E-cadherin expression is typical and relates to reduced cell–cell cohesion.

Dyscohesive tumor cells often infiltrate singly or in linear cords.

Infiltration may induce little desmoplasia and can be difficult to detect radiologically.

Slide 49 · Lobular carcinoma: Single-file invasion

Schematic — not a histologic specimen

Morphologic interpretation

Dyscohesive cells form narrow linear cords within stroma.

Intracytoplasmic mucin may produce signet-ring morphology.

Slide 50 · NST versus invasive lobular carcinoma

NST carcinoma

Irregular glands and cohesive nests

Common desmoplasia

Heterogeneous biomarker patterns

Lobular carcinoma

Single cells / linear cords

Often subtle desmoplasia

Common loss of E-cadherin; Usually luminal

Slide 51 · Lobular carcinoma: Dissemination patterns

Invasive lobular carcinoma may involve peritoneum, retroperitoneum and gastrointestinal tract.

Additional reported sites include leptomeninges, ovaries and uterus.

Such distributions can complicate identification of the breast primary.

Slide 52 · Mucinous carcinoma: Extracellular mucin pools

Schematic — not a histologic specimen

Morphologic interpretation

Rounded nests or clusters of malignant cells reside in large pools of extracellular mucin.

Grossly, the tumor may be soft, gelatinous or rubbery.

Slide 53 · Tubular carcinoma: Highly gland-forming invasion

Schematic — not a histologic specimen

Morphologic interpretation

Small well-formed infiltrating tubules are the central morphologic feature.

Can resemble benign sclerosing lesions; Evidence of invasion is critical.

Slide 54 · Cribriform and papillary invasive carcinomas

Cribriform carcinoma

Invasive nests with sieve-like lumina

Architecture is the defining feature

Typically associated with the luminal group

Papillary carcinoma

True fronds with fibrovascular cores

Distinct from micropapillary spaces

Requires careful invasive versus in situ assessment

Slide 55 · Micropapillary carcinoma: No true fibrovascular cores

Schematic — not a histologic specimen

Morphologic interpretation

Tumor cell clusters appear to float in lacunae or intercellular fluid spaces.

The structures mimic papillae but lack genuine fibrovascular cores.

Slide 56 · Apocrine carcinoma morphology

Tumor cells have abundant eosinophilic, sometimes granular cytoplasm.

Large nuclei and prominent nucleoli contribute to the cytologic appearance.

HER2 overexpression is more common in this special morphologic pattern.

Slide 57 · Metaplastic carcinoma is a broad TNBC-associated group

Neoplastic cells may show squamous or mesenchymal differentiation.

Spindle, chondroid or osseous components can complicate recognition as carcinoma.

Many metaplastic tumors behave aggressively, although some low-grade forms are indolent.

Slide 58 · Salivary gland-like breast carcinomas

Adenoid cystic, secretory and mucoepidermoid carcinomas are uncommon examples.

These tumors resemble counterparts occurring in salivary glands.

Some triple-negative special types have favorable behavior despite absent routine receptors.

Slide 59 · Inflammatory carcinoma: Clinical, not histologic subtype

Schematic — not a histologic specimen

Morphologic interpretation

Extensive dermal lymphovascular tumor emboli impair skin lymphatic drainage.

Rapidly developing erythema, swelling and peau d’orange result.

Slide 60 · Inflammatory carcinoma: Diagnostic pitfall

Erythema and swelling can mimic a breast infection.

The designation refers to a clinical presentation rather than inflammatory histology.

The associated carcinoma is commonly high-grade and diffusely infiltrative.

Slide 61 · Occult primary carcinoma is possible

Nodal or distant metastasis occasionally precedes detection of a breast lesion.

Small primary cancers may be concealed by dense breast tissue or lack desmoplasia.

Targeted ultrasound or MRI may identify a previously occult lesion.

Slide 62 · Biology and extent jointly determine outcome

Molecular or histologic phenotype modifies natural history.

Tumor size, nodal status and metastatic spread capture anatomic extent.

Histologic grade, biomarkers and lymphovascular invasion add information.

Slide 63 · Prognostic versus predictive biomarkers

Prognostic

Associated with likely disease outcome

Example: Tumor size, nodal burden

Can inform counseling and risk

Predictive

Associated with benefit from a specific treatment

Example: ER for endocrine therapy

Can guide treatment selection

Slide 64 · Anatomic progression and prognostic significance

Primary tumor extent

Regional nodes

Distant metastasis

Changing clinical outlook

Distant metastasis is the strongest adverse prognostic element framework.

Slide 65 · Regional lymph nodes: Powerful prognostic variable

In the absence of distant spread, pathologic axillary nodal status is highly informative.

Physical examination alone can miss small deposits or misclassify reactive nodes.

Number and extent of involved nodes matter, not only presence or absence.

Slide 66 · Why sentinel lymph node evaluation works

Breast lymphatic drainage

First-echelon sentinel node

Histologic examination

Axillary staging with less morbidity

A negative sentinel node lowers the probability of additional regional nodal involvement.

Slide 67 · Tumor size and locally advanced disease

Increasing invasive tumor size carries progressively greater risk.

Skin or chest-wall involvement represents advanced local extension.

Larger cancers may be harder to control locally irrespective of molecular subtype.

Slide 68 · Lymphovascular invasion: Tumor within a vessel

Schematic — not a histologic specimen

Morphologic interpretation

True vascular-space invasion represents access to dissemination routes.

It is associated with recurrence risk and poorer outcomes in relevant clinical settings.

Slide 69 · Histologic type and grade modify prognosis

Higher histologic grade is generally associated with worse outcome within stage groups.

Tubular and cribriform subtypes are associated with favorable clinical behavior.

Metaplastic carcinoma encompasses subtypes with substantially different prognoses.

Slide 70 · ER and PR: Separate but related readouts

Estrogen receptor

Nuclear ER expression predicts endocrine responsiveness

Both prognostic and predictive

Intensity and extent carry additional context

Progesterone receptor

Often coexpressed in ER-positive tumors

Low PR can associate with worse outcome

Reflects aspects of hormone-response biology

Slide 71 · HER2 is prognostic and predictive

HER2 positivity is associated with biologically aggressive behavior without effective targeted treatment.

HER2-directed therapies exploit receptor overexpression or amplification.

Biomarker assessment must use validated methods and appropriate interpretation.

Slide 72 · Genomic profiling in selected ER-positive cancers

Proliferation-weighted multigene assays can further stratify prognosis.

Their major clinical value is identifying selected endocrine-responsive cases unlikely to benefit from chemotherapy.

A gene-expression assay does not replace histologic diagnosis and basic receptor assessment.

Slide 73 · Neoadjuvant response has subtype-specific meaning

Pretreatment systemic therapy permits direct assessment of tumor response.

Pathologic complete response is an important prognostic correlate in TNBC and HER2-positive cancers.

The relationship between pathologic response and prognosis is less uniform in luminal cancers.

Slide 74 · Tumor-infiltrating lymphocytes

TILs include lymphocytes and plasma cells in and around tumor-associated stroma.

A brisk infiltrate can reflect an active host antitumor response.

TIL prominence is linked to better neoadjuvant response and prognosis in TNBC and HER2-positive tumors.

Slide 75 · ESR1 mutations and endocrine resistance

ESR1 encodes the estrogen receptor.

Acquired activating alterations can promote ligand-independent ER signaling.

The chapter highlights testing in ER-positive/HER2-negative metastatic disease at endocrine progression.

Slide 76 · Selected predictive molecular alterations

Alteration / biomarker

Pathologic context

Associated therapeutic strategy

BRCA1 or BRCA2 germline variant

Homologous recombination deficiency

PARP inhibitor sensitivity

PIK3CA mutation

ER-positive / HER2-negative cancer

PI3K pathway inhibition

NTRK fusion

Selected secretory carcinomas

NTRK-targeted inhibition

PD-L1 expression

Selected immunotherapy contexts

Checkpoint therapy selection

Slide 77 · Staging: Anatomy versus prognostic integration

Anatomic TNM

Primary tumor extent (T)

Regional nodal burden (N)

Distant metastasis (M)

AJCC 8th prognostic stage

T, N and M

Histologic grade

ER, PR and HER2 (plus select assay data)

Slide 78 · Treatment strategy follows biology and extent

Local control usually involves surgery and, in selected settings, radiation.

Systemic treatment addresses potential or documented distant disease.

Subtype, stage and tumor responsiveness determine the role and timing of systemic therapies.

Slide 79 · Application: Infiltrative glands in a hard mass

Core biopsy shows irregular malignant glands and nests infiltrating a fibrotic stroma. No defining special-type morphology is identified.

Invasive carcinoma of no special type.

Stromal invasion establishes carcinoma; Desmoplasia and disordered glands support the NST morphologic pattern.

Slide 80 · Application: Subtle infiltrative single cells

A poorly defined breast lesion shows rows of isolated, dyscohesive carcinoma cells with loss of E-cadherin expression.

Invasive lobular carcinoma.

The single-file invasive pattern and cell-adhesion phenotype strongly favor lobular carcinoma.

Slide 81 · Application: Rapidly swollen erythematous breast

The skin is diffusely thickened with peau d’orange. Tumor emboli are seen in dermal lymphovascular spaces.

Inflammatory breast carcinoma (clinical presentation).

Dermal lymphatic obstruction explains the skin findings; This is not a distinct underlying histologic tumor type.

Slide 82 · Final synthesis: Integrate four reports

Morphology

Is invasion present?

What histologic type?

What Nottingham grade?

Biology

What are ER, PR and HER2 results?

Are selected additional assays indicated?

Does phenotype alter treatment?

Extent

What is invasive tumor size?

Are nodes involved?

Is there distant spread?

Slide 83 · Core take-home concepts

Invasive carcinoma is defined by stromal invasion—not by a specific cytologic appearance.

Clinical receptor groups and intrinsic expression subtypes are related but nonidentical.

Histologic type, grade, biomarkers and stage provide complementary information.

Accurate morphology and biologic interpretation require clinical–radiologic correlation.

Slide 84 · Source and figure provenance

Primary textbook

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th edition (2026). Chapter 23, The Breast, pp. 954–966.

Source handling

Slides are grounded in the supplied topic Markdown and the adjacent source sections that form its parent context. The original chapter PDF was not provided; page images and textbook figure panels were not independently verified.

Illustration status

Native editable schematics only; no micrograph is presented as an observed specimen.