Gestational Trophoblastic Disease

Slide 1 · Gestational Trophoblastic Disease

Molar pregnancy • pathogenesis • morphology • clinicopathologic interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Classify the major entities in gestational trophoblastic disease.

Derive complete and partial mole genotypes from fertilization events.

Recognize defining gross and microscopic features of molar pregnancy.

Connect hCG behavior and myometrial invasion with clinical follow-up.

Genetic origin

Villous morphology

Clinical behavior

Follow-up interpretation

Schematic

Slide 3 · The defining abnormality is trophoblastic proliferation

Gestational trophoblastic disease (GTD) comprises tumors and tumorlike disorders of placental tissue.

The proliferating tissue is trophoblastic; Chorionic villi may or may not be present.

Morphology and behavior span noninvasive molar lesions through overt malignancy.

Complete / partial mole

Invasive mole

Choriocarcinoma

PSTT / ETT

Schematic

Slide 4 · Classification: The major trophoblastic entities

Entity

Core diagnostic concept

Complete hydatidiform mole

Noninvasive molar pregnancy; exclusively paternal nuclear genome

Partial hydatidiform mole

Noninvasive molar pregnancy; usually triploid

Invasive mole

Hydropic chorionic villi invade the uterine wall

Gestational choriocarcinoma

Malignant trophoblast without chorionic villi

PSTT / ETT

Uncommon extravillous trophoblastic tumors

Slide 5 · Why distinguishing these entities matters

A molar pregnancy must be recognized because persistent trophoblastic disease can follow.

Complete and partial moles differ in genetic origin, morphology, and risk.

Villi within invasive tissue distinguish invasive mole from choriocarcinoma.

Post-evacuation hCG behavior reveals clinically important persistence.

Ultrasound / abnormal pregnancy

Evacuated tissue

Histopathologic interpretation

Serial hCG surveillance

Schematic

Slide 6 · Normal villous architecture provides the reference

Trophoblast covers the chorionic villous core.

Maternal blood surrounds villous surfaces; The villus is a distinct structure.

Interpret trophoblastic growth relative to villous size and shape.

Villous stroma

Schematic

Slide 7 · The histologic unit is the chorionic villus

The villous stroma forms the central core.

Cytotrophoblast and syncytiotrophoblast form trophoblastic components of villous coverings.

Both stromal edema and the pattern of trophoblastic proliferation are needed to interpret molar pathology.

Villous stroma

Schematic

Slide 8 · Hydropic change expands the villous stroma

Excess stromal fluid enlarges villi.

Advanced edema can produce central cavitation (cisterns).

An edematous villus alone does not specify complete versus partial mole.

Expanded edematous stroma

Schematic

Slide 9 · Hydatidiform moles are detected early

Pelvic sonography usually detects molar change in early pregnancy.

A mean gestational age near 9 weeks at diagnosis.

Many early cases are identified following miscarriage or evacuation of abnormal pregnancy tissue.

Ultrasound / abnormal pregnancy

Evacuated tissue

Histopathologic interpretation

Serial hCG surveillance

Schematic

Slide 10 · Distribution varies with reproductive age and geography

Molar pregnancy can occur at any reproductive age.

The risk is increased at the extremes of reproductive life.

Approximately 1 in 1,000–2,000 pregnancies in the United States.

Reported incidence is approximately twice as high in Southeast Asia.

Slide 11 · Two noninvasive molar types

Dimension

Complete mole

Partial mole

Genetic origin

Paternal nuclear genome only

Maternal plus additional paternal genome

Typical ploidy

Diploid

Triploid

Embryonic development

Absent

May occur, abnormal

Villous edema

Most or all villi

Subset of villi

Trophoblast proliferation

Marked, circumferential

Focal, less marked

Slide 12 · Complete mole begins with an “empty” ovum

The ovum lacks a retained maternal nuclear chromosome complement.

The resulting conceptus derives its nuclear genome from paternal chromosomes.

The common event is monospermic fertilization followed by chromosome duplication.

Empty ovum

One sperm

Paternal genome duplication

Paternal diploid (46)

Schematic

Slide 13 · Monospermic complete mole: Androgenesis

Single sperm contributes its haploid genome.

Duplication restores a diploid complement.

The common result is 46,XX with paternal-only nuclear genetic material.

Empty ovum

One sperm

Paternal genome duplication

Paternal diploid (46)

Schematic

Slide 14 · Dispermic complete mole: Two paternal contributions

Two sperm fertilize an ovum lacking maternal nuclear chromosomes.

The resulting complete mole may have 46,XX or 46,XY karyotype.

The nuclear genome remains entirely paternal in origin.

Empty ovum

Two sperm

Dispermic fertilization

Paternal diploid (46)

Schematic

Slide 15 · Most complete moles are 46,XX

Robbins: Approximately 90% are monospermic, androgenetic complete moles.

The remaining approximately 10% are dispermic complete moles.

A diploid chromosome count alone is insufficient to prove a normal biparental conceptus.

Slide 16 · Complete mole: Consequence for embryogenesis

A complete mole does not support embryonic development.

Its growth reflects abnormal placental villi and trophoblast rather than viable embryogenesis.

Absence of embryonic development is one useful discriminator from partial mole.

Slide 17 · Complete mole: Gross appearance

Classic lesions consist of delicate, friable, translucent cystic structures.

Grape-like vesicles correspond to fluid-distended hydropic villi.

The gross pattern is most conspicuous in well-developed lesions.

Grape-like, fluid-distended villi

Schematic

Slide 18 · Complete mole: Diffuse villous enlargement

Most or all villi display edema and enlargement.

Villous profiles tend to be smooth, rounded or oval.

The diffuse distribution matters as much as the abnormality in any single villus.

Diffuse hydropic enlargement

Schematic

Slide 19 · Complete mole: Central cistern formation

Prominent stromal edema may create internal cavitations.

These central cavities are termed cisterns.

Central cavitation complements, but does not replace, evaluation of the trophoblast.

Central cistern

Schematic

Slide 20 · Complete mole: Circumferential trophoblast growth

Trophoblastic proliferation surrounds enlarged villi.

Both cytotrophoblast and syncytiotrophoblast are involved.

The distribution of hyperplasia is characteristically circumferential.

Circumferential growth

Schematic

Slide 21 · Recognizing biphasic proliferation

Cytotrophoblast and syncytiotrophoblast are both increased.

Assess the trophoblastic rim rather than attributing thickening to a single cell type.

This contrasts with the more focal, predominantly syncytiotrophoblastic pattern described in partial mole.

Circumferential growth

Schematic

Slide 22 · Complete mole: Morphology checklist

Component

Expected finding

Villi

Diffuse enlargement; smooth, oval contours

Stroma

Marked edema; central cisterns often evident

Trophoblast

Circumferential, biphasic proliferation

Embryonic structures

No embryonic development

Genetics

Diploid, entirely paternal nuclear genome

Slide 23 · Complete mole: Why hCG is conspicuous

Proliferating trophoblastic tissue produces human chorionic gonadotropin (hCG).

The source describes serum levels greatly exceeding a normal pregnancy at similar gestational age.

The rate of increase can exceed normal singleton or multiple pregnancies.

High hCG relative to gestational age

Serial assessment after evacuation

Persistent elevation → investigate

Schematic

Slide 24 · Complete mole: Complications and persistence

A 15% risk of persistent or invasive mole after a complete mole.

The textbook gives a 2.5% risk of subsequent choriocarcinoma.

These are source-reported estimates, not patient-specific forecasts.

15% persistent / invasive mole

2.5% subsequent choriocarcinoma

Textbook estimates for complete mole

Schematic

Slide 25 · Partial mole: An ovum is fertilized by two sperm

The ovum retains a maternal haploid chromosome set.

Dispermy supplies two additional paternal haploid contributions.

The resulting conceptus is typically triploid.

Ovum: 23 maternal

Two sperm

Dispermic fertilization

Usually triploid (69)

Schematic

Slide 26 · Triploidy is typical of partial hydatidiform mole

Example: 69,XXY

The source also recognizes occasional tetraploid partial moles (e.g., 92,XXXY).

Genetic composition contrasts fundamentally with androgenetic complete mole.

Slide 27 · Partial mole retains a maternal genetic contribution

Complete mole: No maternal nuclear genome retained.

Partial mole: Maternal nuclear chromosomes remain.

This distinction explains why chromosomal counts and parental origin are complementary concepts.

Complete: Paternal only

Partial: Maternal + paternal

Distinct parental origin

Schematic

Slide 28 · Partial mole can show fetal development

Embryonic or fetal development may be present.

The fetus is generally growth restricted.

Severe, lethal central nervous system and skeletal anomalies.

Syndactyly is an example of a skeletal abnormality.

Slide 29 · Partial mole: The edema is heterogeneous

Only a subset of chorionic villi are markedly enlarged.

Other villi can be relatively less affected.

Mixed villous populations are more useful than a single enlarged profile.

Villi of unequal size

Schematic

Slide 30 · Partial mole: Irregular villous contours

Affected villi often have irregular, scalloped outlines.

This differs from the smoother, rounded villi in complete mole.

Evaluate the contour across multiple villi at low power.

Irregular villous contours

Schematic

Slide 31 · Partial mole: Focal trophoblast proliferation

Trophoblastic hyperplasia is relatively mild and patchy.

Syncytiotrophoblastic hyperplasia rather than marked biphasic growth.

Patchiness should not be mistaken for the diffuse complete-mole pattern.

Focal trophoblast growth

Schematic

Slide 32 · Partial mole: Trophoblastic inclusions

Inward folds of trophoblast can be seen within irregular villi.

These are described as prominent trophoblastic inclusions.

Interpret inclusions in combination with scalloping, edema, and growth pattern.

Trophoblastic inclusion

Schematic

Slide 33 · Partial mole: Morphology checklist

Component

Expected finding

Villi

Mixed sizes; only a subset hydropic

Outlines

Irregular, scalloped

Trophoblast

Focal, less pronounced proliferation

Inclusions

Often prominent within villi

Fetal development

May be present but severely abnormal

Genetics

Usually triploid

Slide 34 · Complete vs partial: Genetic differential

Question

Complete mole

Partial mole

Maternal nuclear genome?

Absent

Retained

Paternal contribution

Only paternal chromosomes

Two paternal haploid sets typical

Chromosome complement

46,XX or 46,XY

Usually 69, e.g. XXY

Fetal development

None

Possible but anomalous

Slide 35 · Complete vs partial: Architectural differential

Feature

Complete mole

Partial mole

Extent

Diffuse villous changes

Heterogeneous villous changes

Villus shape

Rounded, oval

Irregular / scalloped

Edema

Marked; cisterns typical

Limited to subset

Hyperplasia

Circumferential; biphasic

Focal; less marked

Inclusions

Not defining feature

Often prominent

Slide 36 · Complete vs partial: Clinical implications

Aspect

Complete mole

Partial mole

Typical hCG behavior

Can be markedly elevated

No quantitative pattern stated here

Pregnancy outcome

No embryo

May show malformed fetus

Postmolar persistence

15% reported for invasive / persistent mole

Risk increased; not quantified here

Choriocarcinoma

Reported subsequent risk

Not typically associated

Slide 37 · Morphology should be read at three scales

Low power: Determine whether edema affects most villi or only a subset.

Intermediate power: Assess rounded versus irregular villous outlines and cisterns.

Higher power: Assess cytotrophoblast/syncytiotrophoblast proliferation and inclusions.

Extent

Contour

Trophoblast

Schematic

Slide 38 · Genetics resolves a distinct diagnostic question

Histology asks how the villi and trophoblast are organized.

Cytogenetic studies ask whether the conceptus is diploid, triploid, or rarely otherwise.

Interpret chromosome complement together with parental nuclear contribution and morphology.

Complete: Paternal only

Partial: Maternal + paternal

Distinct parental origin

Schematic

Slide 39 · A practical interpretation sequence

Establish whether chorionic villi are present.

Characterize the extent and contour of villous hydropic change.

Characterize distribution and cell types of trophoblast proliferation.

Integrate with available clinical and cytogenetic information.

Villous extent and contour

Trophoblast distribution

Genetic information

Integrated diagnosis

Schematic

Slide 40 · The clinical presentation may resemble miscarriage

Early partial and early complete moles commonly present as pregnancy loss.

Alternatively, ultrasound reveals abnormal villous enlargement prompting curettage.

A classic macroscopic grape-like mass is not necessary for early diagnosis.

Ultrasound / abnormal pregnancy

Evacuated tissue

Histopathologic interpretation

Serial hCG surveillance

Schematic

Slide 41 · Sonography identifies abnormal early gestation

Pelvic sonography can disclose abnormal villous enlargement.

Imaging provides a clinical trigger for tissue evacuation and pathologic assessment.

The source does not give sensitivity, specificity, or ultrasound thresholds.

Slide 42 · HCG must be interpreted in temporal context

Complete molar pregnancies can have strikingly high hCG for gestational age.

Persistently elevated hCG after evacuation raises concern for continuing trophoblastic tissue.

Serial measurements assess resolution, not merely the initial concentration.

High hCG relative to gestational age

Serial assessment after evacuation

Persistent elevation → investigate

Schematic

Slide 43 · The post-evacuation pathway

Molar tissue is commonly removed by curettage.

Serial hCG surveillance aims to document return to nonpregnant levels.

Failure to decline appropriately prompts evaluation for persistent disease.

Evacuation of molar tissue

Serial serum hCG

Normalize → resolution

Persistent → investigate

Schematic

Slide 44 · Follow-up duration in the source

Monitoring for 6 months to 1 year after evacuation.

This is a textbook description, not a universal contemporary clinical protocol.

For individual patient management, applicable current regional protocols and risk assessment take priority.

Slide 45 · Persistently elevated hCG requires investigation

The key postmolar warning is biochemical persistence.

Potential explanations in the source include persistent or invasive mole and choriocarcinoma.

Further evaluation and, in some cases, chemotherapy may be required.

Slide 46 · Invasive mole is defined by myometrial penetration

Hydropic chorionic villi breach the normal uterine compartment.

Villi and proliferating trophoblast extend into the myometrium.

Deep extension can occasionally perforate the uterine wall.

Uterine cavity

Myometrium

Hydropic villus crosses boundary

Schematic

Slide 47 · Invasive mole: Three diagnostic anchors

Infiltration of the uterine wall.

Hydropic villi present within invasive tissue.

Proliferating cytotrophoblast and syncytiotrophoblast line the invasive villi.

Uterine cavity

Myometrium

Hydropic villus crosses boundary

Schematic

Slide 48 · Bleeding is linked to destructive local extension

The lesion penetrates myometrial tissue and can involve blood vessels.

Abnormal vaginal bleeding and irregular uterine enlargement can follow.

Serum hCG remains elevated because trophoblastic tissue persists.

Slide 49 · Vascular entry can lead to distant villous emboli

Invasive villi may reach parametrial tissue and maternal blood vessels.

Embolization to distant organs is described in the source.

The lungs and brain are named potential sites.

Uterine cavity

Myometrium

Schematic

Slide 50 · Pulmonary involvement: Interpret the textbook cautiously

Lung lesions in about 5% of complete hydatidiform moles.

Its description of spontaneous regression of small pulmonary lesions is historical textbook context.

Do not use lesion size alone to make current treatment decisions; Specialist staging and protocols are required.

Slide 51 · Invasive mole vs choriocarcinoma

Discriminator

Invasive mole

Choriocarcinoma

Chorionic villi

Present; hydropic

Absent

Trophoblastic pattern

Villi lined by both types

Malignant trophoblastic sheets

Typical tissue effect

Myometrial invasion; villous emboli

Destructive, hemorrhagic invasion

Clinical marker

Persistent hCG elevation

Usually high hCG; exceptions exist

Slide 52 · Choriocarcinoma: Where it fits in the spectrum

A malignant trophoblastic tumor may follow an abnormal or normal pregnancy.

The pathologic lesion consists of malignant trophoblast without villi.

Hemorrhage, necrosis, vascular invasion and distant spread are characteristic.

Its full pathology is addressed in the adjacent dedicated topic.

Slide 53 · Other tumors: Important architectural distinctions

Tumor

Source-described distinguishing feature

Placental site trophoblastic tumor

Mononuclear or binucleated extravillous trophoblast; infiltrates between muscle fibers

Epithelioid trophoblastic tumor

Sheets of mononuclear trophoblast; often clear cytoplasm; hyaline material

Choriocarcinoma

Biphasic malignant trophoblast, no villous structures

Slide 54 · A tissue-centered classification decision

Identify chorionic villi first.

If villi are present, characterize noninvasive versus invasive location.

If villi are absent, evaluate malignant trophoblastic growth and differential diagnosis.

Chorionic villi present?

Villi: Molar / invasive mole

No villi: Consider carcinoma

Correlate clinically

Schematic

Slide 55 · Case 1: Complete mole

Early pregnancy evacuation shows predominantly enlarged oval hydropic villi, central cisterns and circumferential biphasic trophoblast proliferation.

Which molar category best fits, and what nuclear genetic origin is expected?

Complete hydatidiform mole; Entirely paternal nuclear genome, generally diploid.

Slide 56 · Case 2: Partial mole

Evacuated placental tissue contains villi of mixed sizes, scalloped enlarged profiles, trophoblastic inclusions and patchy syncytiotrophoblastic proliferation.

What diagnosis and common ploidy are suggested?

Partial hydatidiform mole; Commonly triploid after dispermy.

Slide 57 · Case 3: Invasive mole

After molar evacuation, serum hCG remains elevated. An infiltrative uterine lesion shows hydropic villi extending into myometrium.

What single morphologic feature favors invasive mole over choriocarcinoma?

Presence of hydropic chorionic villi within the invasive lesion.

Slide 58 · Diagnostic pitfalls: Focus on discriminators

Hydropic enlargement by itself does not establish the genetic subtype.

A partial mole can contain only a minority of conspicuously enlarged villi.

Diffuse versus focal trophoblast proliferation should be assessed across tissue.

Presence or absence of villi is essential in the invasive mole–choriocarcinoma differential.

Extent

Contour

Trophoblast

Schematic

Slide 59 · Clinical red flags after evacuation

Persistent elevation of hCG rather than decline to a nonpregnant level.

New or sustained vaginal bleeding and uterine enlargement.

Findings suspicious for extrauterine trophoblastic disease.

These warrant specialist investigation rather than interpretation from one marker alone.

Slide 60 · Integrating genotype, morphology and behavior

Entity

Genetic clue

Morphology

Behavior

Complete mole

Paternal diploid

Diffuse hydropic villi; circumferential hyperplasia

Risk of persistence

Partial mole

Usually triploid

Scalloped mixed villi; focal growth

Persistent disease possible

Invasive mole

Follows molar disease

Hydropic villi in myometrium

Locally invasive / embolic

Choriocarcinoma

Gestational origin possible

Malignant trophoblast; no villi

Invasive and metastatic

Slide 61 · Four conclusions to retain

Complete mole: Paternal-only diploidy, diffuse hydropic villi, circumferential biphasic trophoblast.

Partial mole: Usual triploidy, variable scalloped villi, focal syncytiotrophoblastic proliferation.

Invasive mole: Hydropic villi penetrate the uterine wall.

Persistent postmolar hCG is a signal for evaluation of ongoing trophoblastic disease.

Genetic origin

Villous morphology

Clinical behavior

Follow-up interpretation

Schematic

Slide 62 · References and limits of this lecture

Primary text: Robbins, Cotran & Kumar, Pathologic Basis of Disease, 11th ed., chapter 22, pp. 939–941.

Classification and numeric estimates are taken from the supplied 2026 textbook extraction.

Source histology figures were not available as reusable image assets; all tissue architecture drawings are original schematics.

The textbook surveillance interval and management descriptions are not substitutes for current local GTD protocols.