FRCPath Pancreas Course

A practical approach

Dr Tu Vinh Luong

Consultant Histopathologist

Wednesday 19th February 2020

Acknowledgments

Many images and tables in this presentation are from Dr Klimstra’s paper (Lab Med—Vol 133, March 2009)

and Dr Hornick’s (Brigham and Women’s Hospital, Harvard Medical School, Boston, MA) lecture

WHO 2019 Classification

Changes since 2010

• Precursors are now classified into two-tiered system of dysplasia:1. Low grade IPMN/mucinous cystic neoplasm/Pan-IN2. High grade IPMN/mucinous cystic neoplasm/Pan-IN

• Classification of pancreatic NENs• New subtype of ductal adenocarcinoma:

micropapillary carcinoma (aggressive clinical course)• Oncocytic-type IPMN is now recognised as a distinct

entity (IOPN)• The only emerging new entity is sclerosing epithelioid

mesenchymal tumour

Abridged classification of pancreatic epithelial neoplasms

ENTITY

• Ductal adenocarcinoma

• IPMN

• Pancreatic NET

• Serous cystadenoma

• Mucinous cystic neoplasm

• Acinar cell carcinoma

• Solid pseudopapillaryneoplasm

• Pancreatoblastoma

Pancreatic neoplasms, %

• 85

• 3-5

• 3-4

• 1-2

• 1-2

• 1-2

• 1-2

• <1

Diagnostic clues from the clinical presentation

• Age

• Sex

• Location

• Symptoms

Algorithm for the diagnostic evaluation of pancreatic neoplasm

Klimstra et al. Arch Pathol Lab Med—Vol 133, March 2009WHO 2010 Classification

First step – Diagnostic algorithmGross appearance

Klimstra et al. Arch Pathol Lab Med—Vol 133, March 2009

Algorithm for the diagnostic evaluation of pancreatic neoplasm

Klimstra et al. Arch Pathol Lab Med—Vol 133, March 2009

Solid neoplasmsNature of epithelium and stroma

<< epithelium / >>stroma >> epithelium / << stroma

Klimstra et al. Arch Pathol Lab Med—Vol 133, March 2009

Ductal adenocarcinoma

Solid neoplasmsPredominant cellular differentiation

Klimstra et al. Arch Pathol Lab Med—Vol 133, March 2009

Acinar cell carcinoma Neuroendocrine neoplasm

Acinar neuroendocrine undetermined

Pancreatoblastoma Solid pseudopapillaryneoplasm

Squamoid nests

yes no

IMMUNOHISTOCHEMISTRY IN THE DIFFERENTIAL DIAGNOSIS OF SOLID CELLULAR PANCREATIC TUMORS

MarkerPoorly Differentiated

Ductal AdenocarcinomaAcinar Cell Carcinoma

PancreatoblastomaPancreatic Endocrine

Tumor

Solid Pseudopapillary

Tumor

Keratin + + + + Rare cells

Chromogranin −Scattered

cellsFocal + −

Synaptophysin −Scattered

cellsFocal + Scattered cells

Trypsin/chymotrypsin − + + − −

Nuclear beta-catenin − SubsetFocal (squamoid

corpuscles)− +

Loss of DPC4 + − − − −

PNET vs PSN

PNET PSN

Algorithm for the diagnostic evaluation of pancreatic neoplasm

Klimstra et al. Arch Pathol Lab Med—Vol 133, March 2009

Cystic neoplasms

? Degenerative changes ? Truly cystic, lined by epithelium

Solid pseudopapillaryneoplasm

Pseudocyst

Cystic lesions of the pancreas

? Degenerative changesTruly cystic, lined by epithelium

Solid pseudopapillaryneoplasm

Pseudocyst

Cystic change in typically solid tumours:- Ductal adenocarcinoma- Cystic pancreatic NET- Cystic acinar neoplasms

Cystic neoplasmsTruly cystic-epithelium lined

Serous

Subepithelial stroma/Relationship to ducts

Serous cystadenoma Mucinous cysticneoplasm

IPMN

Cellular stroma/Separate from ducts

No cellular stroma/Connected to ducts

Mucinous

Serous cystic neoplasms

• Serous cystic neoplasms are the most common type of true cystic neoplasms of the pancreas

• Most serous tumours of the pancreas are benign.• Only rare cases metastasize (serous

cystadenocarcinoma).• Malignancy is defined as metastasis: in the absence of

demonstrable metastases, any typical serous neoplasm should be considered benign.

• ICD-O Code: – Serous cystadenoma 8441/0– Serous cystadenocarccinoma 8441/3

Serous cystadenoma

• Serous cystadenomas arise mostly (50-75%) in the body or tail of the pancreas

• Occur predominantly in women (female-to-male ratio of 3 : 1).

• The mean age of patients at diagnosis is 58 years.

• As many as 90% of patients with VHL syndrome develop serous cystic neoplasms

Serous cystadenoma

The lesion is well circumscribed and composed of small cysts measuring less than 1 cm in the greatest dimension and separated by thin, translucent septa. The innumerable cysts produce a gross appearance resembling that of a sponge.A central, stellate, fibrous scar can be seen.

Serous cystic neoplasm

A. At low power, innumerable small cysts are seen. Each small cyst is lined by a flattened layer of epithelium.

B. At higher power, cytologically, the lining cells show clear cytoplasm and small, uniform, hyperchromatic nuclei. The cells are arranged in a single, flat layer without nuclear atypia

Serous cystic neoplasm

• Histologically and immunophenotypically, all types of serous neoplasms appear to recapitulate centroacinar cells.

• For instance, they express low-molecular-weight keratins, EMA, inhibin, and Melan-A (MART1).

• Molecular genetic alterations include mutations of the von Hippel-Lindau tumour suppressor gene (VHL on chromosome 3p25.3) and allelic losses on chromosome 10q.

• Genetic abnormalities typical of ductal adenocarcinoma (e.g., mutations of KRAS and TP53) have not been identified in serous tumours nor have mutations in GNAS or RNF43, which are found in other cystic or intraductal pancreatic neoplasms

Mucinous cystic neoplasms

• Similar to their serous counterparts, mucinous cystic neoplasms are true cystic neoplasms of the pancreas.

• They are seen almost exclusively in women (with rare examples documented in men; F:M ratio of 20:1) in the fifth to sixth decades of life (mean age, 50 years).

• Patients with MCNs with an associated invasive carcinoma are 5-10 years older, on average, than are patients with non invasive MCNs.

• The tumour usually (>95%) is located in the body and tail of the pancreas.

• Presenting symptoms are nonspecific and are usually the result of the effects of an enlarging mass.

Mucinous cystic neoplasms

• ICD-O-Code:• MCN with low-grade dysplasia 8470/0

• MCN with high-grade dysplasia 8470/2

• MCN with associated invasive

carcinoma 8470/3

• Terms that are no longer to be used:

– Mucinous cystadenoma NOS (not otherwise specified)

– Mucinous cystadenocarcinoma, NOS

Mucinous cystic neoplasm

Distal pancreatectomy showing a circumscribed tumour containing numerous, large (1- to 5-cm) cysts. The septa are fibrotic and show no gross evidence of solid tumour nodules in this example. The cyst contents are often mucoid, but some may have a watery consistency.

Mucinous cystic neoplasm

At low power, the mucinous cysticneoplasm is surrounded by a thick, fibrouscapsule. The large cysts are lined bymucinous epithelium, and the stroma ofthe septa is hypercellular.

At higher magnification, the epitheliallining is composed of tall, columnar,mucin-containing cells. In this region,there is low-grade dysplasia. Thesubepithelial stroma is hypercellular,resembling the stroma of the ovary.

Mucinous cystic neoplasm with an associated invasive carcinoma

(mucinous cystadenocarcinoma)

• Invasive carcinoma may develop in mucinous cystic neoplasms

• Invasive carcinoma arising in a mucinous cystic neoplasm usually resembles conventional pancreatic ductal adenocarcinoma.

• However, other types, such as sarcomatoid carcinoma, or undifferentiated carcinoma with osteoclast-like giant cells, may occur

• Overall, the rate of malignancy in mucinous cystic neoplasms is approximately 10%

• Staging is based on the size of the invasive component

Mucinous cystic neoplasms

• Molecular analysis has disclosed mutations or promoter methylation in many of the genes known to be abnormal in ductal adenocarcinomas, including KRAS, TP53, SMAD4, and CDKN2A.

• Approximately one half of mucinous cystic neoplasms have mutations in RNF43, which codes for a protein with intrinsic E3 ubiquitin ligase activity that is also mutated in IPMNs but not in ductal adenocarcinomas.

• GNAS mutations are not found in mucinous cystic neoplasms, in contrast to IPMNs.

IPMN

• Preoperative differentiation of an intraductalneoplasm from true cystic neoplasms, such as serous or mucinous cystic neoplasms, can be difficult

• Endoscopic findings (e.g., mucin extrusion through the ampulla of Vater) and radiographic findings (e.g., ectasia of the ducts) are diagnostic features.

• Approximately 80% of IPMNs occur in the head of the pancreas.

• Based on the extent of involvement of the ductal system, IPMNs are classified as main duct and branch duct types.

• Branch duct IPMNs may appear as multiple, separate, small cysts grossly and radiographically because of the tortuous nature of the dilated ducts.

• IPMNs are a precursor to and a marker of invasive carcinoma.

• Invasive carcinoma may occur in or distant from the intraductal component.

Intraductal neoplasms are typically cystic radiographically, but are epithelial neoplasms with ductal differentiation that characteristically grow primarily

within the ductal system of the pancreas.

IPMN

Gastric type Pancreatobiliary type Intestinal type

• Low-grade IPMN (previous low and intermediate-grade dysplasia)

• High-grade IPMN

Pancreatic intraductal oncocyticpapillary neoplasm

• Grossly IOPN is a cystic epithelial neoplasm and forms large friable projections or solid nodules within cystically dilated pancreatic ducts

• Microscopically, IOPN forms complex and arborising papillae, lined by 2-5 layers of cuboidal to columnar cells with mitochondrion-rich eosinophilicgranular cytoplasm that contains a large, round nucleus with a prominent nucleolus. Interspersed goblet cells are common. All IOPNs have high-grade dyslasia.

IMMUNOHISTOCHEMICAL PROFILE

Gastric type IPMN Pancreatobiliary type IPMN IOPNIntestinal type IPMN

CK7CK18

+ + + +

CK20 - - + + in goblet cells

MUC1 - + - +

MUC2 - - + + in goblet cells

MUC5AC + + + +

MUC6 -/+ + - +

CDX2 - - + + in goblet cells

CategoryPrevious terminology

and synonymsDescription

Normal Normal ductal and ductular epithelium cuboidal to low columnar.No mucinous cytoplasm, nuclear crowding, or atypia.

PanIN-1A Mucinous cell hyperplasia, mucinous ductal hyperplasia, simple hyperplasia, mucinous hypertrophy

Flat epithelial lesions composed of tall columnar cells with basal nuclei and abundant supranuclear mucin. Nuclei small and round.

PanIN-1B Papillary ductal hyperplasia,adenomatous hyperplasia

Epithelial lesions with papillary, micropapillary, or basally pseudostratified architecture, but otherwise identical to PanIN-1A.

PanIN-2 Adenomatous hyperplasia, atypical hyperplasia Usually papillary mucinous epithelial lesions with

some nuclear abnormalities, including loss of polarity, nuclear crowding, enlarged nuclei, pseudostratification, and hyperchromatism. Mitoses rare.No cribriform structures or luminal necrosis.

PanIN-3 Severe ductal dysplasia, atypical hyperplasia, carcinoma in situ

Usually papillary or micropapillary. Cribriforming, “budding off” of small clusters of epithelial cells into the lumen, or luminal necrosis all suggest PanIN-3. Characterized by loss of nuclear polarity, dystrophic goblet cells, mitoses (occasionally abnormal), nuclear irregularities, and prominent nucleoli.

PANCREATIC INTRAEPITHELIAL NEOPLASIA Pan-IN

Adapted from Hruban et al. Am J Surg Pathol. 2001;25:579-86.

Low grade

High grade

PANCREATIC Pan-IN vs IPMN

Feature PanIN IPMN

Usually clinically detected No Yes

Usually grossly visible No Yes

Usually grossly visible mucin No Yes

Usually well-formed papillae No Yes

MUC2 expression No Often

Loss of DPC4/SMAD4 30% in PanIN-3 Rare

Associated with invasive colloid carcinoma No Yes

Adapted from Hruban et al. Am J Surg Pathol. 2001;25:579-86.

TNM staging of pancreatic exocrine tumours (UICC TNM 8th ed)

UICC/AJCC 7th UICC/AJCC 8th

T1 Confined to pancreas, <2 cm Tumour 2 cm or less in greatest dimension T1a Tumour 0.5 cm or lessT1b Tumour >0.5 cm and no >1cmT1c Tumour >1 cm but no >2cm

T2 Confined to pancreas, >2 cm Tumour >2 cm but < 4 cm

T3 Peripancreatic spread, but without major vascular invasion

Tumour > 4 cm

T4 Invasion of major vessels (coeliac axis or superior mesenteric artery)

Tumour involves coeliac axis, superior mesenteric artery and/or common hepatic artery

N1 Regional LN mets Regional LN metsN1 Metastasis in 1 to 3N1 Metastasis in 4 or more

M1 Distant metastasis Distant metastasis• M1a Hepatic mets only• M1b Extrahepatic mets only• M1c Hepatic and extrahepatic mets

UPDATE ON Pan-NENS

Changes since previous edition

• Tumour classification - WHO 2010 and WHO 2017

• Tumour staging – UICC TNM 8 (2017)

WHO 2010 WHO 2017

UPDATE ON RCPATH DATASET

Revised dataset for histopathological reporting of neuroendocrine neoplasms of the GEP tract - 2019

Evolution in WHO terminology for Pan-NENs

WHO 1980 WHO 2000/2004 WHO 2010 WHO 2017

I. Carcinoid 1. Well-differentiatedendocrine tumour (WDET)

2. Well-differentiated endocrine carcinoma (WDEC)

1. NET G1

2. NET G2

• NET G1

• NET G2

• NET G3

II. Mucocarcinoid 3. Poorly-differentiated endocrine carcinoma/small cell carcinoma (PDEC)

3. NEC G3 (large cell or small cell NEC)

• NEC G3 (large cell or small cell NEC)

III. Mixed formscarcinoid-adenocarcinoma

4. Mixed exocrine-endocrine carcinoma (MEEC)

4. Mixed

adenoneuroendocrine

carcinoma (MANEC)

Mixed

neuroendocrine/non

neuroendocrine

neoplasm (MiNEN)

IV. Pseudotumourlesion

5. Tumour-like leisons (TLL) 5. Hyperplastic and preneoplastic lesions

Abolished preneoplastic

category, because PanNEN

precursor changes have not been

clearly identified in association

with sporadic neoplasms

Tumour type and differentiation

Regardless of the site there are three major tumour types:

• well-differentiated NETs

• poorly differentiated NECs

• Mixed tumours or MiNENs

Terminology

• NET is a well-differentiated epithelial neoplasm with morphological and immunohistochemical features of neuroendocrine differentiation

• NETs can be low-grade (G1), intermediate-grade (G2) or high-grade (G3) tumours

• NEC is a poorly differentiated epithelial neoplasm with morphological and immunohistochemical features of neuroendocrine differentiation

• NEC is, by definition, high grade (for this reason, the WHO 2019 classification proposed not to assign a grade to NECs, whereas previously all NECs were graded G3)

Terminology

• There is no ‘well-differentiated neuroendocrine carcinoma’ category

• The term ‘NEN’ encompasses all well-differentiated and poorly differentiated tumours of the neuroendocrine cells

• MiNEN is a mixed epithelial neoplasm in which a neuroendocrine component is combined with a non-neuroendocrine component, each of which is morphologically and immunohistochemically recognisable as a discrete component and constitutes ≥30% of the neoplasm.

MiNENMixed neuroendocrine-non neuroendocrine neoplasms

• New term MiNEN replaces previous term MANEC

• MiNENs may have a non-endocrine component other than adenocarcinoma (e.g. squamous cell carcinoma, acinar cell carcinoma)

• To qualify as MiNEN each component must have at least 30~%

• Usually both components are high grade (G3), but occasionally one of the two or both components may belong to the G1/G2 category. When the components are morphologically distinguishable, they should be individually graded, using the respective grading systems for each.

An adenocarcinoma showing scattered neuroendocrine cells, demonstrated using anti-chromogranin A antibody, cannot be classified as a MiNEN

WHO 2017 PanNEN classification and WHO 2010 Pan-NEN classification

WHO 2017 pancreatic-NEN Classification WHO 2010 GEP-NEN Classification

Well-differentiated NETs

• NET G1

• NET G2

• NET G3

Well-differentiated NETs

• NET G1

• NET G2

Poorly differentiated NECs

• NEC G3 (large cell or small cell NEC)

Poorly differentiated NECs

• NEC G3 (large cell or small cell NEC)

Mixed neuroendocrine-non neuroendocrine

neoplasm (MiNEN)

Mixed adenoneuroendocrine carcinoma

(MANEC)

Abolished category, because PanNEN precursor

changes have not been clearly identified in

association with sporadic neoplasms2

Hyperplastic and preneoplastic lesions

2017 WHO classification of pancreatic NENs

Classification/grade Ki-67 proliferation index Mitotic index

• Well-differentiated PanNENs: pancreatic neuroendocrine tumours (PanNETs)

PanNET G1 <3% <2

PanNET G2 3-20% 2-20

PanNET G3 >20% >20

• Poorly-differentiated PanNENs: pancreatic neuroendocrine carcinomas (PanNECs)

PanNEC (G3)Small cell typeLarge cell type

>20% >20

• Mixed neuroendocrine-non neuroendocrine neoplasm (MiNEN)

TUMOUR GRADING

New recommendations for reporting Ki67

• The Ki-67 is based on the evaluation of >= 500 cells

• Assess hotspots (areas with higher nuclear labelling)

• Round up or down to the nearest whole number

• If mitotic count and Ki67 are discordant, the final grade is determined based on whichever index (Ki-67 or mitotic) places the tumour in the highest grade category

• Manual counting using camera-captured, printed images is recommended instead of casual visual estimation or eyeballing.

Pancreatic NENS with a Ki-67-index >20%

NET G3 NEC G3

Differentiation Well-differentiated Poorly-differentiated

Ki-67 >20%, no defined upper limit, butusually <55%

>20%, usually >55%

Mutations MEN1, DAXX, ATRX p53, RB1

p53 Focal, weak positivity Diffuse, strong positivity

SSTR2A 3+ 2+/1+/- (80%)

NET G3 NEC G3

Pancreatic NENS with a Ki-67-index >20%

Günter Klöppel, 2016 IAP-ESP presentation

ENETS vs UICC 7th vs UICC 8th TNM of the pancreas

54

ENETS UICC/AJCC 7th UICC/AJCC 8th

T1 Confined to pancreas, <2 cm Confined to pancreas, <2 cm Confined to pancreas*, 2 cm or less

T2 Confined to pancreas, 2–4 cm Confined to pancreas, >2 cm Confined to pancreas *>2 cm but < 4 cm

T3 Confined to pancreas, >4 cm or invading duodenum or bile duct

Peripancreatic spread, but without major vascular invasion

Confined to pancreas*, > 4 cmor invading duodenum or bile duct

T4 Invasion of adjacent organs (stomach, spleen, colon, adrenal gland) or the wall of large vessels (celiac axis or superior mesenteric artery)

Invasion of major vessels (coeliac axis or superior mesenteric artery)

Tumour perforates visceral peritoneum (serosa) or invades other organs or adjacent structures

N1 Regional LN mets Regional LN mets Regional LN mets

M1 Distant metastasis Distant metastasis Distant metastasis• M1a Hepatic mets only• M1b Extrahepatic mets

only• M1c Hepatic and

extrahepatic mets

* Confined to the pancreas means there is no invasion of adjacent organs (stomach, spleen, colon, adrenal gland) or the wall of large vessels (celiac axis or the superior mesenteric artery). Extension of tumour into peripancreatic adipose tissue is NOT a basis for staging.

Exceptions to the simplified algorithmic scheme

• Rare neoplasms (undifferentiated carcinoma with osteoclasticlike giant cells, medullary carcinoma, intraductal tubular carcinoma,lymphoepithelial cyst …)

• Common neoplasms with unusual features(solid variant of serous cystadenoma, ductal adenocarcinoma and NETs with cystic changes…)

• Carcinoma with mixed differentiation(acinar-endocrine, ductal-endocrine, acinar-ductal…)

• Metastatic disease(lung, kidney, ovary, breast and melanoma)

Serous cystadenoma in communication with the pancreatic duct

Berman L. J Clin Gastroenterol. 2010 Jul;44(6)

PD

PD

FRCPath Pancreas Course

Frozen sections

Commonest indications for

intraoperative frozen section diagnosis

• Histological confirmation of a potentially

metastatic nodule in the liver, peritoneum or

a lymph node

• Histological confirmation of the primary

diagnosis

• Assessment of the presence or absence of

carcinoma at the pancreatic transection

margin,

• Assessment of the presence or absence of

carcinoma at the bile duct margin

Diagnostic challenges

• Distinction between a liver metastasis

and a bile duct hamartoma/adenoma

may prove problematic

• Distinction between pancreatitis and

adenocarcinoma in the pancreas may

also be difficult on frozen section,

because of cautery or freezing

artefacts, or the distortion and reactive

nuclear atypia in small residual ductules

in chronic pancreatitis

Chronic pancreatitis vs Adenocarcinoma

Low power

- Retention of lobular arrangement (circles): larger, dilated central ducts surrounded by smaller, round ductules. The interlobular stroma is denser than the intralobular stroma

-Disorganized ductal distribution /lack of a lobular configuration- Abnormal location (perineural, adjacent to a muscular vessel, “naked glands” in fat, within duodenal muscularis)

Chronic pancreatitis vs Adenocarcinoma

High power

- Limited nuclear size variation - Slight nuclear irregularity - Inconspicuous nucleoli - Hyperchromatism represents a frozen section artifact

- Anisonucleosis (more than 4-fold nuclear variation)- Necrotic glandular debris - Partial duct lumen - Infiltrating single cells - Glandular mitotic figures (arrows)

FEATURES FAVORING PANCREATIC DUCTAL ADENOCARCINOMAIN FROZEN SECTIONS AND BIOPSIES

Feature Benign Malignant

Lobular configuration of ducts + −

Haphazard distribution of ducts − +

Incomplete duct lumina − +

Single atypical cells in stroma − +

Nuclear size variation 4:1 − +

Large, irregular nucleoli − +

Necrotic luminal debris − +

Glandular mitoses − +

Perineural invasion − +

Glands in adipose tissue − +

VHL positivity + -

Maspin positivity − +

p53 positivity − +

Mesothelin positivity − +

Loss of DPC4/SMAD4 − +