Pancreatoblastoma

Slide 1 · Pancreatoblastoma

A malignant pediatric pancreatic tumor defined by acinar and squamoid differentiation

Morphology • Wnt biology • diagnosis • management

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Identify the clinicopathologic profile of pancreatoblastoma

Recognize diagnostic squamoid corpuscles in acinar-pattern tumors

Construct a defensible differential and multidisciplinary work-up

Relate molecular features and extent of disease to clinical decisions

Slide 3 · Four anchors

01

Predominantly affects children aged 1–15 years

02

Squamous islands intermingle with acinar cells

03

Malignant behavior, but outcomes exceed pancreatic ductal adenocarcinoma

04

Frequent activation of the Wnt signaling pathway

Slide 4 · Cell lineage frames the differential

Exocrine acinar cells synthesize digestive enzymes

Ductal epithelium forms the pancreatic drainage network

Endocrine islet cells produce peptide hormones

A tumor may show more than one differentiation pattern

Acinar

Digestive enzymes

Ductal

Drainage epithelium

Endocrine

Hormone production

Slide 5 · Which pancreatic masses occur in children?

Entity

Useful diagnostic orientation

Pancreatoblastoma

Acinar differentiation + squamoid corpuscles

Solid pseudopapillary neoplasm

Solid/cystic, pseudopapillary architecture

Neuroendocrine tumor

Neuroendocrine morphology and markers

Ductal carcinoma

Malignant ductal glands with desmoplasia

Slide 6 · Rare overall, important in young children

Pediatric pancreatic malignancies are uncommon

Pancreatoblastoma accounts for a meaningful share of childhood pancreatic tumors

Relative frequency within pediatric pancreatic tumors is not population incidence

10–20%

Of childhood pancreatic tumors in the NCI PDQ summary; Denominator matters.

Slide 7 · Age is a powerful clinical clue

Presentation from 1 to 15 years

Contemporary pediatric series show a median diagnosis age around 4–5 years

Occurrence in adults is documented, so age alone cannot establish or exclude the diagnosis

Infancy

Early childhood

Adolescence

Rare adult cases

Slide 8 · The Beckwith–Wiedemann association

Beckwith–Wiedemann syndrome increases pancreatoblastoma risk

Syndromic context is particularly relevant in very early-onset tumors

Constitutional predisposition should prompt genetics input when indicated

Overgrowth syndrome

Cancer predisposition

Early pancreatic mass

Genetic evaluation

Slide 9 · Familial adenomatous polyposis is another clue

Association with familial adenomatous polyposis has been reported

The APC pathway links this association biologically to Wnt signaling

This is an association—not evidence that most cases are hereditary

APC dysfunction

Wnt dysregulation

Pancreatoblastoma association

Slide 10 · Embryonal differentiation: A working model

Pancreatoblastoma has an embryonal/fetal-acinar phenotype

Tumor cells can display acinar, solid, and trabecular organization

Normal developmental identity may be altered rather than simply retained

Embryonal phenotype

Acinar features

Heterogeneous patterns

Slide 11 · The molecular theme is Wnt activation

Recurrent Wnt-pathway activating alterations

CTNNB1 encodes β-catenin, a transcriptional co-regulator

Abnormal β-catenin signaling is mechanistically relevant, not a stand-alone diagnosis

Wnt-pathway alteration

β-catenin stabilization

Transcriptional effects

Slide 12 · Canonical Wnt signaling: An overview

With low Wnt activity, the destruction complex limits β-catenin accumulation

Wnt receptor signaling suppresses β-catenin destruction

Stabilized β-catenin can enter the nucleus and alter target transcription

Wnt OFF

Active destruction complex

β-catenin degraded

Wnt ON

Destruction complex inhibited

β-catenin stabilized

Nucleus

Accumulated β-catenin

Transcriptional response

Slide 13 · CTNNB1 alterations

Somatic CTNNB1 variants can stabilize β-catenin signaling

NCI PDQ identifies CTNNB1 as a common mechanism of Wnt activation in pancreatoblastoma

A pathway alteration does not uniquely identify a pancreatic tumor subtype

CTNNB1 activating variant

Reduced β-catenin turnover

Wnt target-gene signaling

Slide 14 · APC connects genotype with pathway

APC is part of the β-catenin destruction machinery

Loss of its suppressive function can raise β-catenin pathway activity

Robbins also describes APC or CTNNB1 alterations in acinar cell carcinoma

APC loss of function

β-catenin dysregulation

Shared molecular pathway

Slide 15 · IGF2 alterations are another recurrent finding

NCI PDQ describes frequent IGF2 gene alterations

These alterations coexist with a proposed disturbance of pancreas differentiation

Avoid translating this observation into an unproven clinical treatment target

Wnt signaling

IGF2 alteration

Cell differentiation

Slide 16 · Molecular overlap is not diagnostic identity

Finding

Interpretation

Wnt-pathway alteration

Supports pathway biology, not unique identity

Acinar marker positivity

Supports exocrine acinar differentiation

Squamoid corpuscles

Strong morphologic clue to pancreatoblastoma

Slide 17 · Clinical presentation may be deceptively bland

A large palpable abdominal mass can be the presenting finding

Abdominal pain or fullness is nonspecific

Some children have little symptom burden despite a sizable neoplasm

Expanding mass

Abdominal enlargement

Clinical detection

Slide 18 · Common symptoms arise from local mass effect

Abdominal pain, vomiting, anorexia, and weight change may occur

Symptoms depend on size, location, and surrounding anatomy

None of these features is specific for pancreatoblastoma

Compression

Displacement

Variable symptoms

Slide 19 · Jaundice is surprisingly uncommon

Observation

Teaching implication

Head/neck pancreatic location

Does not guarantee duct obstruction

No clinical jaundice

Cannot exclude a pancreatic tumor

Biliary obstruction

Evaluate anatomy on cross-sectional imaging

Slide 20 · AFP: Useful but not universal

Approximately 70–80% of pediatric pancreatoblastomas have elevated or secreted AFP

AFP helps support a suspicion when morphology and imaging fit

Normal AFP does not rule out pancreatoblastoma

~70–80%

Reported proportion with elevated/secreted AFP; Not diagnostic sensitivity in an unselected population.

Slide 21 · AFP supports response assessment

Document the pretreatment AFP value when elevated

Falling AFP may corroborate treatment response

A subsequent rise can trigger evaluation for recurrence

Interpret serial values alongside imaging and clinical status

Baseline AFP

Therapy

Serial AFP + imaging

Recurrence assessment

Slide 22 · AFP is not a tumor-specific stain

AFP can be elevated in other pediatric tumors and conditions

Biochemical evidence must be integrated with pancreatic origin

A positive AFP result cannot replace tissue diagnosis

Serum marker

Anatomic imaging

Pathology

Slide 23 · Unusual secretory manifestations

Ectopic hormone

Possible manifestation

ACTH

Cushing syndrome

Antidiuretic hormone

SIADH

Slide 24 · Metastatic disease matters at diagnosis

Metastases may be present when pancreatoblastoma is first recognized

Liver, lymph nodes, and lungs are reported sites

Tumor extent modifies surgical planning and overall prognosis

Pancreatic primary

Regional assessment

Liver and nodes

Thoracic evaluation

Slide 25 · Imaging establishes origin and extent

Ultrasound may identify a heterogeneous abdominal mass

Contrast-enhanced CT or MRI clarifies pancreatic origin and local relations

Chest imaging is relevant when metastatic evaluation is indicated

US detection

CT / MRI mapping

Metastatic survey

Team planning

Slide 26 · Imaging appearance is heterogeneous

Large masses may show mixed solid and cystic components

Fibrous septa, hemorrhage, or necrosis contribute to heterogeneity

Radiologic appearance alone cannot establish histologic subtype

Solid tumor

Fibrous septa

Cystic/necrotic change

Slide 27 · Imaging cannot show a squamoid corpuscle

Imaging can assess

Histology must assess

Pancreatic origin and local invasion

Acinar differentiation

Vascular and organ relationships

Squamoid islands

Possible metastases

Neoplastic cell phenotype

Slide 28 · Macroscopy: A lobulated mass

Pancreatoblastomas may form large, soft, circumscribed lesions

Fibrous partitions can divide the mass into lobules

Hemorrhage, necrosis, and variable cystic change may occur

Lobules separated by broad fibrous partitions

Schematic — not a photomicrograph

Slide 29 · Gross appearance is not a diagnosis

Circumscription does not prove benign behavior

Cystic degeneration can resemble other pediatric pancreatic lesions

Sample solid areas, interface, and heterogeneous regions appropriately

Gross sampling

Microarchitecture

Final classification

Slide 30 · Microscopic architecture: Lobules and bands

Cell-rich lobules can be separated by broad fibrous septa

Acinar, trabecular, and solid patterns can coexist

This heterogeneity makes low-power architectural review useful

Fibrous partitions between lobules

Schematic — not a photomicrograph

Slide 31 · Acinar differentiation is the epithelial backbone

Neoplastic cells may organize around small luminal spaces

Cytoplasm can have granular eosinophilic character

Acinar architecture alone is not specific for pancreatoblastoma

Central acinar lumen

Schematic — not a photomicrograph

Slide 32 · Squamoid corpuscles are the diagnostic pivot

Pale squamoid islands occur among the acinar-pattern tumor cells

They may form compact nests or whorled groups

Their recognition is particularly helpful against acinar cell carcinoma

Squamoid focus

Schematic — not a photomicrograph

Slide 33 · What “squamoid” means here

The corpuscles represent an unusual epithelial differentiation focus

They need not resemble an overt invasive squamous carcinoma

Interpret them within the surrounding acinar neoplastic architecture

Fibrous partitions between lobules

Schematic — not a photomicrograph

Slide 34 · Sampling: The danger of a small biopsy

Squamoid nests may be sparse or absent from a limited core

An acinar-rich core can resemble acinar cell carcinoma

Correlate multiple levels and broader sampling with the clinical setting

Small core

Acinar-only appearance

Expand sampling

Seek squamoid foci

Slide 35 · Acinar markers confirm differentiation

Marker

Role

Trypsin

Acinar differentiation

Chymotrypsin

Acinar differentiation

BCL10

Acinar differentiation

Slide 36 · β-catenin staining requires localization

Aberrant nuclear labeling can occur in squamoid corpuscles

Cytoplasmic staining alone should not be equated with pathway activation

The distribution of labeling across components can be informative

Tumor component

Subcellular location

Integrated interpretation

Slide 37 · Neuroendocrine markers can mislead

Finding

Correct response

Focal synaptophysin

Assess full architecture

Focal chromogranin

Check extent and other lineage markers

Acinar + squamoid pattern

Maintain pancreatoblastoma in differential

Slide 38 · A disciplined immunohistochemistry strategy

First, establish epithelial and acinar differentiation

Then inspect squamoid foci and β-catenin localization

Use neuroendocrine markers to test mixed differentiation

Avoid interpreting any single marker in isolation

Morphology

Acinar stains

Squamoid / β-catenin

Integrated report

Slide 39 · Primary differential: Acinar cell carcinoma

Pancreatoblastoma

Acinar cell carcinoma

Childhood predominance

Usually adult presentation

Squamoid corpuscles characteristic

Squamoid corpuscles usually absent

Acinar markers positive

Acinar markers positive

Wnt activation frequent

Wnt alterations also described

Slide 40 · Solid pseudopapillary neoplasm: Major mimic

Pancreatoblastoma

Solid pseudopapillary neoplasm

Acinar + squamoid

Pseudopapillary structures

AFP often elevated

AFP generally normal

Malignant pediatric embryonal tumor

Usually indolent / low-grade behavior

Slide 41 · Neuroendocrine tumor: Lineage over focal stains

Question

Discriminating clue

Dominant lineage?

Acinar vs neuroendocrine

Squamoid nests?

Support pancreatoblastoma

Marker distribution?

Focal versus extensive endocrine pattern

Slide 42 · Ductal adenocarcinoma: A different architecture

Pancreatoblastoma

Ductal adenocarcinoma

Acinar + squamoid

Infiltrative malignant ducts

Usually pediatric

Predominantly older adults

Distinct molecular context

KRAS, TP53, CDKN2A, SMAD4 in Robbins

Slide 43 · An AFP-positive hepatic mass requires care

Pancreatoblastoma can metastasize to the liver

AFP elevation may suggest an embryonal tumor elsewhere

Correlate liver findings with pancreatic imaging and tissue phenotype

Do not infer primary organ solely from a serum marker

Liver lesion + AFP

Find primary site

Compare morphology

Integrated diagnosis

Slide 44 · Discordant findings should trigger review

Young child + large pancreatic mass may favor pancreatoblastoma

Limited tissue without squamoid nests may remain ambiguous

Shared molecular findings do not settle acinar versus pseudopapillary lineage

Escalate to additional sections or expert consultation when needed

Clinicoradiology

Tissue review

Targeted stains

Expert integration

Slide 45 · A practical diagnostic algorithm

Confirm pancreatic origin and tumor extent

Examine low-power architecture and targeted squamoid nests

Use acinar and other lineage markers judiciously

Reconcile age, AFP, morphology, and molecular findings

Pancreatic mass

Acinar / squamoid review

Lineage stains

Integrated classification

Slide 46 · Tumor classification precedes management

Pancreatoblastoma is malignant despite occasional circumscription

Resectability and metastases are distinct from tumor identity

Extent and histologic subtype must both be communicated

Histologic identity

Extent of disease

Treatment plan

Slide 47 · Resectability is a multidisciplinary decision

Surgical planning considers vascular and adjacent-organ involvement

Cross-sectional imaging informs feasibility and expected morbidity

Rare pediatric pancreatic tumors warrant specialist team review

Imaging extent

Surgeon assessment

Pathology input

Pediatric tumor board

Slide 48 · Pathology reporting after resection

Record anatomic location, size, and adjacent-tissue involvement

Document resection margins and sampled regional lymph nodes

Report differentiation, squamoid foci, and relevant ancillary results

Use the actual institutional protocol; Do not invent entity-specific staging cutoffs

Slide 49 · Localized disease: Complete resection matters

NCI PDQ identifies surgery as the main treatment modality

Complete resection is central to cure when technically feasible

Pancreaticoduodenectomy may be required for head-region lesions

Localized lesion

Complete excision if feasible

Pathologic margin review

Follow-up

Slide 50 · Unresectable disease: Chemotherapy may help

Larger or initially unresectable tumors may receive neoadjuvant chemotherapy

Pediatric literature commonly uses cisplatin-containing regimens

Response may permit reassessment for definitive surgery

Initially unresectable

Systemic therapy

Reimage / reassess

Potential resection

Slide 51 · Metastatic disease requires individual planning

Management commonly combines systemic therapy and surgery when appropriate

Stage and organ involvement guide multidisciplinary decisions

Published estimates come from small heterogeneous pediatric cohorts

Systemic disease

Local control

Long-term assessment

Slide 52 · Treatment evidence has important limits

Better established

More uncertain

Value of complete resection

Optimal radiation strategy

Activity of cisplatin regimens

Best salvage drug sequence

Need for specialist center

Reliable comparisons among small series

Slide 53 · How prognosis differs from ductal carcinoma

Favorable context

Higher-risk context

Completely resected localized tumor

Residual / unresectable tumor

No metastases

Metastatic presentation

Coordinated multimodal care

Limited response or recurrence

Slide 54 · Post-treatment surveillance is multimodal

Track clinical symptoms and physical findings

Measure serial AFP only when informative at baseline

Use cross-sectional imaging appropriate to disease and treatment course

Interpret discordant AFP and imaging results cautiously

Clinical review

AFP if informative

Imaging

Re-evaluation

Slide 55 · Hypothetical case: Child with abdominal mass

A 5-year-old has progressive abdominal enlargement

Imaging identifies a pancreatic-origin solid mass

Serum AFP is elevated

Biopsy shows acinar differentiation and squamoid islands

Clinical question

Which two microscopic findings are most decisive for classification?

Slide 56 · Case interpretation: Phenotype over a marker

Acinar differentiation establishes an exocrine pancreatic component

Squamoid islands strongly support pancreatoblastoma

Elevated AFP supports the clinical picture but is not definitive

Disease extent still needs assessment

Acinar phenotype

Squamoid islands

Pancreatoblastoma

Slide 57 · Hypothetical case: An adolescent pancreatic mass

An adolescent has a mixed solid-cystic pancreatic lesion

Biopsy shows pseudopapillary structures

There are no convincing acinar structures or squamoid corpuscles

Nuclear β-catenin is present

Clinical question

Which diagnosis should be high in the differential?

Slide 58 · Case interpretation: Shared β-catenin biology

Finding

Weight

Pseudopapillary architecture

Strongly favors SPN

No squamoid corpuscles

Weakens pancreatoblastoma

Nuclear β-catenin

Seen in both; not decisive

Slide 59 · Hypothetical case: Tiny acinar-positive core

A young child has a large pancreatic mass

The core biopsy is trypsin-positive but lacks squamoid foci

Clinical and imaging findings still raise pancreatoblastoma

The initial differential includes acinar cell carcinoma

Clinical question

What is the appropriate next pathology step?

Slide 60 · Case interpretation: Recognize sampling error

Request deeper sections or more representative tissue where feasible

Review architecture for focal squamoid islands

Correlate AFP, age, imaging, and directed stains

Do not force a definitive subtype from inadequate material

Limited tissue

Broader sampling

Integrated review

Defensible diagnosis

Slide 61 · What an expert must communicate

01

Pancreatoblastoma is a distinct malignant pediatric pancreatic tumor

02

The key histologic combination is squamoid + acinar differentiation

03

Wnt activation is common but not exclusive

04

Extent, resection status, and AFP trends influence care

Slide 62 · References and evidence boundaries

Robbins, Cotran & Kumar: Pathologic Basis of Disease, 11th ed. (2026), ch. 19, p. 812

NCI PDQ: Childhood Pancreatic Cancer Treatment, Health Professional Version (consulted 2026)

Patterson KN et al. Front Pediatr. 2022;10:966943 (CC BY)

Primary Robbins passage is short; expanded content is independently sourced in speaker notes