Differentiation and Anaplasia

Slide 1 · Differentiation and Anaplasia

Neoplastic resemblance, cytologic atypia and tumor function

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Define tumor differentiation using both morphology and function.

Recognize cellular, nuclear, mitotic and architectural features of anaplasia.

Interpret differentiation without equating it with benign or malignant status.

Explain why some tumors retain normal products while others secrete unexpected proteins.

Classification of a tumor requires more than a single microscopic feature.

Slide 3 · Differentiation: The reference is normal tissue

Differentiation asks how closely neoplastic parenchymal cells resemble their normal counterpart.

Resemblance may involve cell shape, tissue organization and specialized activity.

The appropriate comparison depends on the cell or tissue of origin.

Compare tumor cells with the correct normal lineage.

Slide 4 · Tumor parenchyma and stroma have different roles

Neoplastic parenchyma

Constitutes the tumor cell population

Principal basis for tumor classification

The component evaluated for differentiation

Reactive stroma

Provides connective tissue and blood vessels

Includes immune and other supporting cells

Supports growth but is not the differentiation reference

Slide 5 · Morphologic and functional resemblance are distinct

Morphology

Cell and nuclear form

Preservation of glandular or squamous patterns

Architecture and orientation

Function

Production of normal tissue products

Hormonal or secretory specialization

Loss or alteration in anaplastic tumors

Slide 6 · Differentiation is a spectrum, not a switch

Well differentiated

Close resemblance to normal morphology and function

Moderately differentiated

Recognizable but irregular lineage features

Poorly differentiated / anaplastic

Little or no normal resemblance

Descriptive continuum: No universal numeric boundaries are asserted here

Slide 7 · Benign tumors generally resemble their tissue of origin

Benign neoplasms are almost always well differentiated.

Their constituent cells may be nearly indistinguishable from normal counterparts.

The abnormality may be recognized primarily by formation of a localized mass.

Benignity does not require bizarre cytology.

Slide 8 · A lipoma can look like normal adipose tissue

Lipoma consists of benign adipocytes that resemble mature fat cells.

Individual cells may be difficult to recognize as neoplastic.

The discrete aggregate of cells establishes the lesion as a tumor.

SCHEMATIC — not a photomicrograph

Mature-appearing adipocytes: Simplified schematic

Slide 9 · Neoplastic identity is not always a cytologic diagnosis

Individual adipocyte

Mature appearing

Little or no atypia

May look entirely normal

Mass of adipocytes

A discrete growth

Localized proliferation

Neoplastic nature evident at tissue level

Slide 10 · Thyroid follicular adenoma retains follicular architecture

Benign thyroid follicular adenoma exhibits well-formed follicles.

The follicles may contain colloid and resemble normal thyroid tissue.

This illustrates substantial tissue-specific differentiation.

SCHEMATIC — not a histologic specimen

Regular colloid-containing follicles

Slide 11 · Mitotic figures in well-differentiated benign tumors

Mitoses are usually infrequent in well-differentiated benign tumors.

When observed, they usually have a normal configuration.

This tendency is helpful context, not a universal diagnostic rule.

Mitotic count alone never substitutes for full tumor assessment.

Slide 12 · Malignancy can coexist with substantial differentiation

High differentiation

Normal-like cellular features

May preserve tissue architecture

Specialized products may be retained

Malignant behavior

Tumor invades surrounding structures

Tumor may metastasize

Bland cytology does not establish benignity

Slide 13 · A differentiated thyroid carcinoma can form follicles

Some thyroid adenocarcinomas form follicles resembling those of normal thyroid.

Preserved follicles demonstrate differentiation, not necessarily benignity.

Invasion and metastatic capability establish malignant behavior.

SCHEMATIC — not a histologic specimen

Regular colloid-containing follicles

Slide 14 · Squamous differentiation may produce keratin pearls

Well-differentiated squamous cell carcinomas may form keratin pearls.

Keratin production recapitulates the function of mature squamous cells.

Keratinization can coexist with malignant invasive growth.

Concentric keratinization: Conceptual pearl

SCHEMATIC — not a histologic specimen

Slide 15 · Tissue resemblance and invasion answer different questions

Differentiation

Benign behavior

Malignant behavior

Well differentiated

Common (e.g., lipoma)

Possible despite bland cells

Poorly differentiated / anaplastic

Not a characteristic benign pattern

Strongly suggests malignancy

Key distinction

Localized, usually noninvasive

Invasion and metastatic potential

The two dimensions are related but not interchangeable.

Slide 16 · Moderate differentiation retains recognizable lineage features

Moderately differentiated tumors lie between the well-differentiated and anaplastic extremes.

Some characteristic structures remain, but are distorted or incomplete.

This descriptive category does not replace evaluation of invasion.

“Moderate” describes resemblance—not a standalone behavior test.

Slide 17 · Colon adenocarcinoma may form irregular glands

Moderately differentiated colon adenocarcinoma may retain gland formation.

Malignant glands vary in size and shape and depart from normal colonic architecture.

The Robbins example invades the colonic muscular layer.

SCHEMATIC — not a histologic specimen

Irregular gland-like profiles

Slide 18 · Recognizing residual glandular differentiation

Normal-like glands

Relatively uniform size and shape

Ordered relationship to surrounding tissue

Architecture resembles site of origin

Malignant differentiated glands

Glands are distorted and irregular

Tissue arrangement is abnormal

The lesion may invade deeper layers

Slide 19 · Differentiation should not be used as a binary label

Descriptive position

Typical morphologic idea

Diagnostic limitation

Well differentiated

Close resemblance to normal tissue

Can still be malignant

Moderately differentiated

Some characteristic structures remain

Cannot infer extent of spread

Anaplastic / undifferentiated

Little resemblance to normal tissue

Suggests malignancy; site may be unclear

Slide 20 · The most anaplastic tumors lose normal resemblance

Poorly differentiated tumors show only limited lineage-specific morphology.

Highly anaplastic tumors may appear undifferentiated.

Anaplasia is strongly associated with malignant behavior.

SCHEMATIC — not a photomicrograph

Marked pleomorphism with enlarged nuclei

Slide 21 · Anaplasia is a cellular phenotype, not a tumor name

Anaplasia refers to lack of differentiation.

It is recognized through characteristic cytologic and architectural abnormalities.

Its prominence varies; Not every malignant tumor is markedly anaplastic.

Anaplasia predicts malignancy, but its absence does not exclude cancer.

Slide 22 · A morphologic survey has several independent axes

Domain

Morphologic finding

Meaning

Cell population

Pleomorphism

Marked variation among tumor cells

Nucleus

Enlargement, hyperchromasia, nucleoli

Nuclear atypia

Cell division

Atypical mitotic forms

Abnormal mitotic configuration

Architecture

Loss of polarity

Disordered orientation and growth

Tumor environment

Ischemic necrosis

Vascular support may lag behind growth

Slide 23 · Pleomorphism means variable cell size and shape

Pleomorphism describes nonuniform tumor cells within a single lesion.

Cells may range from small, relatively primitive-appearing forms to very large cells.

Variation in form is more conspicuous in many anaplastic tumors.

SCHEMATIC — not a photomicrograph

Variation in cell size and form

Slide 24 · Cell-size variation is a direct visual clue

A uniform cell population has a relatively narrow range of forms.

Pleomorphic tumors contain visibly different cell sizes and contours.

Morphologic variation is assessed across the field, not from one isolated cell.

SCHEMATIC — not a photomicrograph

Variation in cell size

Slide 25 · Nuclear pleomorphism can exceed cellular variation

Tumor nuclei may differ markedly in size and shape.

Some cells contain extraordinarily large or distorted nuclei.

Nuclear atypia is assessed together with cytoplasm and architecture.

SCHEMATIC — not a photomicrograph

Nuclear size variation

Slide 26 · Tumor giant cells are extreme examples of pleomorphism

Anaplastic tumors may contain cells far larger than their neighbors.

One tumor giant cell may have a single huge, bizarre nucleus.

Others contain two or more large, hyperchromatic nuclei.

SCHEMATIC — not a photomicrograph

Very large tumor cell beside smaller cells

Slide 27 · Do not mistake tumor giant cells for macrophage giant cells

Tumor giant cell

Often has bizarre giant nuclei

May have one huge polymorphic nucleus

May contain multiple large atypical nuclei

Inflammatory giant cell

Macrophage-derived

Langhans or foreign body type

Contains numerous small, relatively normal nuclei

Slide 28 · Nuclear-to-cytoplasmic ratio often increases

Anaplastic nuclei can occupy a disproportionate fraction of the cell.

Ratios approaching 1:1 in cancer cells.

The cited normal comparison is approximately 1:4 to 1:6.

Ratio is a morphologic clue—not a universal numerical threshold.

Slide 29 · Large nuclei change the balance of the cell

Relatively small nucleus

Disproportionately large nucleus

Normal comparator: N:C ≈ 1:4 to 1:6

Cancer cells may approach N:C ≈ 1:1

SCHEMATIC — ratios are textual examples, not drawn to scale

Slide 30 · Irregular nuclear contours suggest atypia

Cancer cell nuclei may have variable, irregular shapes.

Compare the nuclear outline across multiple cells.

Irregularity gains diagnostic weight alongside other abnormal findings.

SCHEMATIC — not a photomicrograph

Schematic variable nuclear outlines

Slide 31 · Hyperchromasia reflects darker nuclear staining

Hyperchromatic nuclei stain more darkly than expected.

Coarse chromatin and increased nuclear darkness.

Color intensity is considered with nuclear size and shape.

SCHEMATIC — not a photomicrograph

Darkened nuclei (conceptual color only)

Slide 32 · Chromatin may be coarsely clumped

Anaplastic nuclei may have coarse, irregularly distributed chromatin.

Chromatin often appears concentrated near the nuclear membrane.

This differs from a fine, relatively even chromatin pattern.

SCHEMATIC — not a photomicrograph

Coarse chromatin (conceptual simplified)

Slide 33 · Prominent nucleoli are another nuclear abnormality

Abnormally large nucleoli are common in many cancer cells.

Nucleolar prominence should be interpreted in overall nuclear context.

No single nucleolar appearance independently establishes malignancy.

SCHEMATIC — not a photomicrograph

Visible nucleoli (small white markers)

Slide 34 · Read nuclear atypia as a constellation

Feature

What to look for

Interpret with

High N:C ratio

Nucleus dominates cytoplasm

Cell type and context

Irregular contour

Variable or angulated outline

Pleomorphism

Hyperchromasia

Darkly staining nuclei

Chromatin pattern

Coarse chromatin

Clumping, peripheral accentuation

Nucleoli and contours

Large nucleoli

Conspicuous nuclear structures

Other malignant features

Slide 35 · Mitoses may be numerous in undifferentiated cancer

Undifferentiated malignancies frequently have abundant mitotic figures.

This finding reflects active tumor cell proliferation.

The number of mitoses must be assessed with the wider histologic picture.

High mitotic activity is common in some cancers, but not synonymous with cancer.

Slide 36 · Mitosis itself is not evidence of malignancy

Nonmalignant proliferating tissues

Intestinal epithelium normally renews rapidly

Hyperplasia may contain many mitoses

Mitoses may have normal configuration

Malignant lesions

Some cancers show numerous mitoses

Others are well differentiated with fewer

Atypical configurations are more concerning

Slide 37 · Atypical mitotic figures are more informative

Anaplastic malignancies may contain bizarre mitotic configurations.

A multipolar or tripolar spindle is an example illustrated by Robbins.

Atypical shape is more concerning than mitotic presence alone.

Three spindle poles (tripolar)

SCHEMATIC — not a mitotic micrograph

Slide 38 · Mitotic quantity and mitotic quality differ

Observation

What it indicates

What it does not establish

Many ordinary mitoses

Active cell turnover

Malignancy by itself

Few ordinary mitoses

Low observed mitotic activity

Definite benignity

Bizarre multipolar mitosis

Abnormal cell division pattern

Tumor type without context

Slide 39 · Loss of polarity is architectural, not merely nuclear

Normal epithelial cells have an ordered orientation to each other and to basement membranes.

Anaplastic tumors may lose this spatial organization.

Tumor cells then grow as disorganized sheets or masses.

Loss of polarity is a tissue-level feature of anaplasia.

Slide 40 · Ordered epithelium versus disrupted polarity

Orderly epithelial orientation

Basement membrane

Disordered tumor cell orientation

Basement membrane

SCHEMATIC — simplified cell orientation, not a tissue section

Slide 41 · Architectural disorder complements cytologic atypia

Cytologic examination

Nuclear shape and size

Chromatin and nucleoli

Cellular pleomorphism

Architectural examination

Cell orientation and polarity

Gland or sheet organization

Relationship to basement membrane

Slide 42 · Ischemic necrosis may appear within rapidly growing tumors

Growing tumor cells require an adequate blood supply.

Vascular stroma may not keep pace with rapid cancer growth.

Insufficient perfusion can produce ischemic necrosis.

Vascular support

Central ischemic area

SCHEMATIC — not a specimen

Slide 43 · Tumor growth and vascular support can become mismatched

Tumor expands

Increasing metabolically active cell mass

Vascular support lags

Stromal supply is inadequate

Focal ischemia

Areas of tumor necrosis emerge

Slide 44 · Necrosis is contextual—not a stand-alone cancer test

Ischemic necrosis among changes found in rapidly growing cancers.

Its presence should be integrated with cytonuclear and architectural findings.

The broader diagnostic question remains tumor identity and invasive behavior.

Do not infer a histologic grade from necrosis alone.

Slide 45 · Use a structured assessment of anaplastic morphology

Start with

Ask

Then inspect

Cellular variation

Are cells uniform or pleomorphic?

Giant tumor cells

Nuclear detail

Are contours, chromatin and nucleoli atypical?

N:C ratio

Division

Are mitoses atypical?

Multipolar figures

Architecture

Is polarity retained?

Ordered tissue organization

Stroma

Is perfusion visibly insufficient?

Ischemic necrosis

Slide 46 · Differentiation has a functional dimension

Normal cell lineage

Characteristic differentiated activity

Well-differentiated tumor

Activity may be retained

Anaplastic tumor

Activity often diminished or absent

Slide 47 · Well-differentiated endocrine tumors may secrete hormones

Endocrine neoplasms may retain the specialized secretory function of their tissue.

The secreted hormone may be measurable in the circulation.

Such measurements can help identify tumors and follow therapeutic response.

Function can be diagnostically informative when it is retained.

Slide 48 · Keratin production reflects squamous differentiation

Cellular identity

Squamous lineage

Terminal maturation may be recognizable

Keratin is a specialized product

Tumor interpretation

Keratinization signals differentiation

Keratin pearls may occur in carcinoma

Invasion still determines malignancy

Slide 49 · Bile production reflects hepatocellular differentiation

Well-differentiated hepatocellular carcinomas may elaborate bile.

The product reflects a retained function of hepatocytes.

Functional resemblance may persist despite malignant behavior.

A retained normal product is not proof of benignity.

Slide 50 · Loss of specialization accompanies marked anaplasia

Well-differentiated neoplasm

Often resembles original cells

May retain normal products

Lineage may be recognizable

Highly anaplastic neoplasm

Typically loses specialized activity

May lack obvious mature architecture

May express unexpected proteins

Slide 51 · Cancer cells may express unusual proteins

Highly anaplastic cells can acquire features absent from the normal adult lineage.

Some tumors express fetal proteins not made by corresponding mature cells.

Others express proteins associated with a different cell type.

Abnormal functional expression broadens the tumor phenotype.

Slide 52 · Bronchogenic carcinomas can secrete ectopic hormones

Unexpected product mentioned by Robbins

Interpretive concept

Corticotropin

Hormone production outside normal source

Parathyroid-like hormone

Ectopic hormone-related activity

Insulin

Unexpected endocrine phenotype

Glucagon

Unexpected endocrine phenotype

Slide 53 · Ectopic secretion can cause paraneoplastic syndromes

Bronchogenic carcinoma

Expression of an unexpected hormone

Circulating product

Physiologic effect distant from tumor

Paraneoplastic syndrome

Clinical manifestation due to secretion

Slide 54 · Morphology and function need not move together

Morphologic context

Illustrative product

Interpretive implication

Well-differentiated squamous carcinoma

Keratin

Retained lineage-specific function

Well-differentiated hepatocellular carcinoma

Bile

Retained lineage-specific function

Well-differentiated endocrine tumor

Native hormone

May aid diagnosis and follow-up

Highly anaplastic neoplasm

Absent or unexpected secretion

Specialization may be lost or redirected

Slide 55 · Growth rate alone cannot reliably separate benign from malignant

Malignant tumors tend, on average, to grow faster than benign tumors.

There are important exceptions across both groups.

Growth rate as an unreliable sole discriminator.

Growth kinetics cannot replace pathologic assessment.

Slide 56 · A differentiated appearance does not exclude invasion

Well-differentiated malignant cells can resemble normal mature cells.

Their malignant nature may be established by invasion of adjacent tissues.

The capacity to metastasize further distinguishes malignant behavior.

Do not diagnose benignity solely from bland cytology.

Slide 57 · Distinguishing differentiation from malignant behavior

Evaluate differentiation

Does tumor resemble its normal lineage?

Evaluate anatomic interface

Does tumor infiltrate neighboring tissue?

Interpret together

A differentiated neoplasm can still be malignant

Slide 58 · Clinical interpretation: Bland adipocytes in a mass

Apply the morphologic principles

A discrete soft-tissue lesion is composed of mature, uniform adipocytes. Individual cells resemble normal adipose tissue. What establishes that it is a neoplastic lesion?

Reason from the findings; No additional case data are assumed.

Slide 59 · Application: Identify the lesion at tissue level

The discrete mass of otherwise mature-appearing adipocytes supports a lipoma. Individual bland cell appearance alone need not reveal neoplasia.

The tissue-level growth pattern matters.

Differentiation is high; Pleomorphism is not required.

This does not imply all fatty masses are automatically benign.

Slide 60 · Clinical interpretation: Distorted colon glands

Apply the morphologic principles

A colonic tumor contains gland-forming epithelium, but the glands are irregular and infiltrate the muscular layer. How is differentiation described, and why is this malignant?

Reason from the findings; No additional case data are assumed.

Slide 61 · Application: Gland formation and invasion are compatible

Residual gland formation supports moderate differentiation; Invasive growth into the muscular layer demonstrates malignant behavior.

Glandular architecture is preserved only in part.

Irregular gland shape signals morphologic departure from normal.

Differentiation and invasion answer different questions.

Slide 62 · Clinical interpretation: Many mitoses in the intestine

Apply the morphologic principles

A sample of rapidly renewing intestinal epithelium has numerous mitoses. Can the presence of mitoses alone establish malignancy?

Reason from the findings; No additional case data are assumed.

Slide 63 · Application: Proliferation is not the same as anaplasia

No. Normal intestinal epithelium and hyperplastic tissues may have many mitoses. Bizarre atypical figures and other abnormalities are more concerning.

Confirm the cell population and tissue context.

Inspect mitotic configuration, not just frequency.

Evaluate architecture and accompanying nuclear features.

Slide 64 · Case integration: Pleomorphic cells with tripolar mitoses

Apply the morphologic principles

A tumor shows extreme nuclear size variation, hyperchromatic nuclei, loss of polarity and a tripolar mitotic figure. Which morphologic concept unifies these findings?

Reason from the findings; No additional case data are assumed.

Slide 65 · Application: The defining pattern is anaplasia

The combined pattern indicates marked anaplasia: Lack of differentiation with nuclear atypia, pleomorphism and disordered cell division and architecture.

Atypical mitosis is particularly informative.

Multiple concordant findings strengthen interpretation.

Additional evidence still establishes exact tumor lineage and extent.

Slide 66 · Interpretation checklist for tumor differentiation

Question

Finding supporting differentiation

Finding supporting anaplasia

Does it resemble origin?

Recognizable tissue-specific structures

Little resemblance

Are cells uniform?

Bland, similar-looking cells

Marked pleomorphism

Are nuclei mature appearing?

Relatively normal morphology

High N:C ratio, irregular contours

Are divisions ordinary?

Infrequent, typical figures

Bizarre atypical mitoses

Is orientation retained?

Ordered polarity

Disorganized growth

Is function retained?

Characteristic secretions/products

Lost or unexpected products

Slide 67 · Central conclusions

Differentiation measures morphologic and functional resemblance to normal lineage.

Anaplasia describes loss of differentiation and a constellation of cytologic and architectural abnormalities.

Well-differentiated tumors can be malignant; Invasion and metastasis remain decisive behavioral features.

Functional retention or ectopic secretion can be diagnostically and clinically significant.

Interpret phenotype, architecture and behavior together.

Slide 68 · Reference and source limitations

Primary source

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th edition (2026).

Chapter 7, Neoplasia: “Differentiation and Anaplasia,” printed pages 239–241.

Parent context: “Characteristics of Benign and Malignant Neoplasms,” page 239.

Schematic figures in this lecture are not diagnostic specimens.