ORIGINAL ARTICLE

Immunohistochemical Antibody Panel for the Differential
Diagnosis of Pancreatic Ductal Carcinoma From
Gastrointestinal Contamination and Benign Pancreatic
Duct Epithelium in Endoscopic Ultrasound-Guided
Fine-Needle Aspiration
Ayako Furuhata, CT, IAC,*† Sachiko Minamiguchi, MD, PhD,* Hiroyuki Shirahase, CT, IAC,*
Yuzo Kodama, MD, PhD,‡ Souichi Adachi, MD, PhD,† Takaki Sakurai, MD, PhD,*
and Hironori Haga, MD, PhD*

Objectives: The diagnosis of pancreatic ductal adenocarcinoma (PDAC)
by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) can
be challenging to distinguish tumor cells from benign epithelium (BE).
The aim of the present study was to set a minimal antibody panel to differentiate PDAC from contaminated BE in EUS-FNA specimens.
Methods: Immunohistochemistry using claudin 4, EZH2, Ki-67, maspin,
p53, and S100P was performed on tissue microarray sections containing 53
PDACs and 33 BE as well as cell blocks of EUS-FNA including 53 PDACs
and 22 BE. The positive rate was scored as 0 to 4+. The receiver operating
characteristic curve was applied to determine a cutoff point, and the Classification And Regression Trees method was used to obtain a classification
tree of the best panel.
Results: The cutoff point was 1+ for claudin 4, EZH2, Ki-67, p53, and
S100P and 2+ for maspin. All BE scored 0 for p53. The classification tree
revealed using p53, S100P, and claudin 4 was the most powerful. The sensitivity and specificity of the tree were 96.2% and 100% in tissue microarrays and 100% and 95.5% in EUS-FNA, respectively.
Conclusions: The classification tree using p53, S100P, and claudin 4
seems to successfully distinguish PDAC from the accompanying BE.
Key Words: endoscopic ultrasound-guided fine-needle aspiration,
tissue microarray, immunohistochemical panel, cell block,pancreatic ductal adenocarcinoma(Pancreas 2017;46: 531–538)

E

ndoscopic ultrasound-guided fine-needle aspiration (EUSFNA) for pancreatic lesions is a safe and efficient procedureand has become a popular approach for the diagnosis of pancreatictumors.1,2 The sensitivity of a cytological diagnosis in EUS-FNA(91.5%) for pancreatic ductal adenocarcinoma (PDAC) was previously reported to be higher than that of pancreatic juice (21.3%)
and brushing cytology (48%),1,3 and the number of cases undergoing EUS-FNA has been increasing in our institute. Recent studies reported the potential of neoadjuvant therapy to decrease thesize of tumors and make them more resectable4,5; therefore, a
From the *Department of Diagnostic Pathology, †Human Health Sciences, and‡Department of Gastroenterology and Hepatology, Kyoto University Graduate
School of Medicine, Kyoto, Japan.
Received for publication February 17, 2016; accepted October 6, 2016.
Address correspondence to: Sachiko Minamiguchi, MD, PhD, Department
of Diagnostic Pathology, Kyoto University Hospital, 54 Shogoin
Kawahara-cho, Sakyo-ku, Kyoto, 606–8507 Japan(e‐mail: minami@kuhp.kyoto-u.ac.jp).
The authors declare no conflict of interest.
Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
DOI: 10.1097/MPA.0000000000000774

Pancreas • Volume 46, Number 4, April 2017

definite diagnosis of PDAC in EUS-FNA is important for all patients with PDAC. The EUS-FNA has the ability to accurately diagnose high-grade PDAC; however, well-differentiated PDAC can
be challenging because it shows low to moderate N/C ratio, honeycomb structure with mild loss of polarity, low-grade nuclear
atypia, and is difficult to distinguish from contaminated benign
gastrointestinal epithelium or benign or reactive pancreatic ductal
cells, which are present with pancreatitis.6
In addition to a cytological diagnosis, the usefulness of cell
blocks in EUS-FNA using immunohistochemical staining withvarious antibodies has recently been reported.1,6–9 Potential markers
for PDAC include enhancer of zeste homologue 2 (EZH2), claudin
4, S100P, Ki-67, and p53.1,6–17
The EZH2 is a methyltransferase at lysine 27 of histone
H3 and is also a member of the developmentally related polycomb
repressor complex.10 An increase in the expression of EZH2 hasbeen detected in a number of carcinomas including PDAC andcholangiolocellular carcinoma.10–12
Claudin 4 is a protein involved in the formation of tight junctions. Its overexpression has been detected in PDAC, breast cancer, and ovarian cancer by gene profiling.13 Furthermore, theoverexpression of claudin 4 in pancreatic intraepithelial neoplasia
and its relationship with intraductal papillary mucinous neoplasms (IPMNs) have also been reported.14–16 However, the expression of claudin 4 in PDAC has not yet been examined
immunohistochemically using EUS-FNA.
Maspin is a member of the serpin superfamily of serine proteinase inhibitors. Its expression has been reported by using immunohistochemical studies of PDAC and high-grade intraductal
dysplasia.17 The diagnostic utility of surgical pathology specimens and tissue cell blocks obtained by EUS-FNA has been reported for maspin as well as Ki-67 and p53.8,9,17
The S100P is a member of the S100 family of calciumbinding proteins and promotes cancer progression via specificroles in survival, cell proliferation, invasion, and metastasis
through its extracellular functions.6 The expression of S100P in
PDAC has been examined in detail in surgical specimens and
EUS-FNA samples.6,9 However, the accuracy of these antibodies
alone is not 100%, and studies that have specifically focused on
distinguishing PDAC from BE are very limited.
Therefore, the aim of the present study was to assess immunostaining patterns and results using the antibodies described previously and identify the optimal antibody panel asan adjunctive diagnostic tool, particularly for a differential diagnosis between PDAC and BE including a benign pancreatic ductal epithelium and contaminated gastric/duodenal epithelium in
EUS-FNA material.
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MATERIALS AND METHODS
Cytological Smears and Tissue Cell Blocks
Seventy-five cases underwent EUS-FNA for pancreatic lesions at Kyoto University Hospital between August 2010 andJune 2014. The PDAC cases were confirmed by a histological diagnosis from the resected pancreas, and benign cases were clinically confirmed by imaging studies and/or the clinical coursewith a follow-up duration of more than 9 months. We performed
rapid onsite evaluation for all EUS-FNA cases and confirmed
the puncture site. The EUS-FNA was performed only for solidmass. Intraductal papillary mucinous neoplasms and mucinous
cystic tumors showing cystic lesions on image analysis are excluded from the subject for EUS-FNA. A 22-gauge needle wasused for EUS-FNA. Samples were obtained and prepared for
Diff-Quik stain for rapid on-site cytology to assure the quantityand quality of the material, whereas the remainder was wetfixed for Papanicolaou staining. In addition, tissue fragments were
fixed in 10% neutral-buffered formalin, embedded in paraffin,
and then processed as a routine tissue block. Tissue sections fromthe cell block were stained with hematoxylin-eosin (HE) and used

for immunohistochemistry. We prepared the cell blocks for all of
the 75 EUS-FNA cases.
The study was approved by the Institutional Review Boardof the Committee for Human Right in Research of Kyoto
University Hospital.

Tissue Microarrays
Our tissue microarray (TMA) series consisted of PDAC cases(n = 53) and BE including benign pancreatic ducts (n = 10), benign
gastric mucosa (n = 11), and benign duodenal mucosa (n = 12).
The TMA blocks were constructed from archival, formalinfixed, and paraffin-embedded tissues. The diameter of all cores
was 2 mm.

Immunohistochemical Analysis
Immunohistochemical staining was performed using paraffinembedded cell blocks.
We selected claudin 4 (clone 3E2C1, 1:100; Invitrogen Corporation, Carlsbad, Calif ), EZH2 (clone D2C9, 1:50; Cell Signaling
Technology, Danvers, Mass), Ki-67 (clone MIB-1, 1:300; Dako
North America, Inc, Carpinteria, Calif ), maspin (clone G167–70,

FIGURE 1. Immunostaining of PDAC, benign pancreatic duct, and gastric and duodenal mucosa with 6 markers (EZH2, S100P Ki-67, maspin,
p53, and claudin 4). EZH2 and Ki-67 exhibit nuclear staining in PDAC and gastric/duodenal mucosa and are negative in the benign
pancreatic duct. S100P showed nuclear and cytoplasmic staining in PDAC and the gastric mucosa and is negative in the benign pancreatic
duct and duodenal mucosa. p53 showed nuclear staining in PDAC but is negative in the nonneoplastic epithelium of any type. Maspin
showed nuclear and cytoplasmic staining in PDAC and a few cases of the duodenal mucosa and is negative in the benign pancreatic duct andgastric mucosa. Claudin 4 showed circumferential staining in PDAC, no staining in the gastric mucosa, and discontinuous staining in the
benign pancreatic duct and duodenal mucosa.

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Pancreas • Volume 46, Number 4, April 2017

1:1000; Becton Dickinson Immunocytometry Systems, San Jose,
Calif ), p53 (clone DO-7, 1:200; Dako North America, Inc), and
S100P (clone 16/f5, 1:100; Ventana Medical Systems, Tucson,Ariz) as diagnostic markers. Immunostaining on cell blocks using
the aforementioned antibodies was performed on the Ventana
BenchMark URTLA instrument (Ventana Medical Systems). Nuclear staining for EZH2, Ki-67, and p53; membranous staining forclaudin 4; membranous and cytoplasmic staining for maspin; andnuclear and cytoplasmic staining for S100P were regarded as positive. In the present study, immunostaining results for all but
claudin 4 were scored as 0 (<5% of cells stained), 1+ (5%–25%), 2+ (26%–50%), 3+ (51%–75%), and 4+ (>75%). Regarding the membranous staining of claudin 4, scores were gradedas 0 (no staining), 1+ (weak discontinuous staining), 2+ (weak circumferential staining), and 3+ (strong discontinuous or circumferential staining). Discordant cases were reviewed by 3 pathologists(S.M., T.S., and H.H.) using a multiheaded microscope, and consensus was reached.

Antibody Panel for PDAC and Benign Epithelium

PDAC and BE. All statistical analyses were performed with
EZR (Saitama Medical Center, Jichi Medical University, Saitama,
Japan), which is a graphical user interface for R (The R Foundation for Statistical Computing, version 3.2.1, Vienna, Austria).18

Classification Tree
A classification tree was constructed using the Classification And Regression Trees (CART) method (Salford Predictive
Modeler v7.0; Salford Systems, San Diego, Calif ) based on the
results of TMAs. We used GINI splitting criterion to measurequality of a split. Briefly, the distinction between PDAC and
BE was set as the target, and the 6 antibodies were used as predictors. Parent node minimum cases were set as 10, and terminal
node minimum cases as 1. The minimum-cost tree, that is, with thelowest level of classification errors, was the best tree. A 10-foldcross validation was used for testing.

RESULTS

P53 Large-Section Validation
To evaluate the p53 heterogeneity of BE, we performed p53
immunostaining on specimens of resected material, which was
also used in TMA. Five blocks of different PDAC cases including
benign pancreatic ducts and gastric and duodenal mucosa were selected. We selected 5 spots from each section and counted cells
exhibiting positivity for p53.

Statistical Analysis
We used the receiver operating characteristic (ROC) curve todetermine an appropriate cutoff point to discriminate between

Immunohistochemical Staining Patterns on TMAs
A photomicrograph of each marker in PDAC and BE on
TMAs is shown in Figure 1. The ROC analysis revealed a cutoff
point of 1+ for claudin 4, EZH2, Ki-67, p53, and S100P and 2+
for maspin (Fig. 2 and Table 1). The area under the curve (AUC)
represents an optimal summary statistic for comparing sensitivities and specificities. Therefore, the cutoff values, sensitivities,
and specificities for each marker were estimated at the highest
AUC. Table 2 summarizes the staining results for 6 markers:
claudin 4, EZH2, Ki-67, maspin, p53, and S100P.

FIGURE 2. The ROC curve analysis for each of the 6 antibodies evaluated.
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TABLE 1. Predictive Value of Each Marker
Cutoff Value Specificity Sensitivity AUC
p53
Maspin
S100P
claudin 4
Ki-67
EZH2

1+
2+
1+
1+
1+
1+

1
0.97
0.667
0.333
0.333
0.303

0.528
0.396
0.849
0.962
0.528
0.962

95% CI

0.764 0.696–0.832
0.713 0.616–0.81
0.765 0.662–0.868
0.683 0.572–0.794
0.333 0.211–0.455
0.595 0.469–0.721

CI indicates confidence interval.

We observed the following features in the BE: (1) A score ofmore than 0 for p53 was not observed in the BE of any type;(2) Scores of more than 0 for S100P were noted in some benign
gastric epithelium; (3) Scores of more than 0 for claudin 4 or
maspin were observed in some benign pancreatic ductal and duodenal epithelium; and (4) Scores of more than 0 for EZH2 andKi-67 were observed in all types of epithelium.

Classification TreeA CART analysis was performed to select the best subset
among the 6 antibodies tested for discriminating PDAC from
BE. The analysis showed 4- (using p53, S100P, and claudin
4) and 5-node (using p53, S100P, claudin 4, and maspin) classification trees (Fig. 3a, b upper). Prediction and misclassification foreach node were also shown (Fig. 3a, b lower). In PDAC cases, theerror rate of the 4- and 5-node classification trees was 3.8%. Two
misclassified PDAC cases were apparently malignant both on cytology and cell block preparations.
In benign cases, the 4-node classification tree had a lower error rate than that of the 5-node tree (0% vs 3.8%).

Final Diagnosis and Cytological Diagnosis of
EUS-FNA Materials
In histological diagnoses of the resected pancreas, all 53
cases were diagnosed as PDAC, and the 22 benign cases included 14 benign pancreatic ducts, 5 gastric mucosa, and 3
duodenal mucosa.
We used 4 categories, benign, atypical, suspicious, and malignant, as the reporting system of EUS-FNA. The original cytological diagnoses of 48 of 53 PDAC cases were malignant, with
1 and 4 cases being diagnosed as atypical and suspicious, respectively. All 22 benign cases were benign (Table 3).

Diagnostic Value Using the Classification Tree in
TMA and EUS-FNA Specimens
The sensitivity and specificity of the classification tree forthe diagnosis of PDAC were 96.2% and 100% in TMAs and100% and 95.5% in EUS-FNA, respectively (Table 4). Although
we originally achieved higher sensitivities and specificities incytology and cell blocks in EUS-FNA, sensitivities and specificities of 100% were observed in combination with the classification tree (Table 5).
One case of PDAC with a cytological diagnosis of “atypical”
included only a few clusters of 1 cell block preparation and was
positive for p53 (Fig. 4).

p53 Large-Section Validation
The positivity of p53 in the resected specimen for the benign
pancreatic ducts and gastric and duodenal mucosae was less than
5% in all spots, and these results were the same as those of
TMAs (Table 6).

DISCUSSION
Although EUS-FNA is an excellent tool for diagnosing
pancreatic cancer, false negatives and a cytological diagnosis
of “atypical” remain issues because of the underestimation ofwell-differentiated adenocarcinoma and/or cases with little content. These cases are difficult to distinguish from contamination
by benign gastric/duodenal mucosa or pancreatic cells by cytology only, and we need to evaluate cytological and cell block preparations together for EUS-FNA.19
Although many antibodies have been investigated for PDAC
in EUS-FNA samples, previous studies that have focused on the
diagnostic pitfalls of contamination of gastric/duodenal mucosa
are very limited. Therefore, further studies are needed to identify
useful markers for distinguishing PDAC from BE.
We herein analyzed 6 proteins, which have been reported to
be overexpressed in PDAC. S100P, maspin, p53, and Ki-67 arerecognized as good markers for diagnosing PDAC in cell blockspecimens obtained by EUS-FNA.8,9 Liu et al9 demonstrated
strong or diffuse staining (>75% or 51%-75% of tumor cells
stained) for S100P and maspin in all 44 EUS-FNA specimensfrom PDAC. However, they also revealed that the expression of
S100P was frequently positive in the gastric mucosa, and maspin
was expressed in the normal gastric antral and fundic mucosa as
well as duodenal mucosa.
Jahng et al8 reported that p53 and Ki-67 have the potential to
improve the sensitivity of EUS-FNA in diagnosing PDAC. In theirstudy, positive staining of more than 50% of cells was considered
to be malignant, and 14/49 and 20/49 PDAC cases were positive
for p53 and Ki-67, respectively.8 However, we considered that thiscutoff point (50%) was relatively high on the limited amount oftissue collected from EUS-FNA, and additional studies based on
ROC analyses are needed to determine the cutoff levels for p53
in our study. Few studies have been conducted on EZH2 andclaudin 4 in PDAC. Gao et al11 reported the immunohistochemical positivity of EZH2 in EUS-FNA in 31/38 samples of PDAC.
Our preliminary study revealed that EZH2 was expressed in thegastric mucosa. In previous studies, the cutoff points of themarkers differed from each other, and immunostaining patterns
in all contaminated epithelial samples (pancreatic ducts andgastric/duodenal mucosa) were not analyzed. Furthermore, theTABLE 2. Immunohistochemical Staining of PDAC and Benign Epithelia in TMAs

PDAC (n = 53)
BE (n = 33)
Pancreatic duct (n = 10)
Gastric mucosa (n = 11)
Duodenal mucosa (n = 12)534

EZH2 (%)

S100P (%)

Ki-67 (%)

Maspin (%)

p53 (%)

Claudin 4 (%)

51/53 (96)23/33 (70)0/10 (0)11/11 (100)12/12 (100)45/53 (85)
11/33 (33)
0/10 (0)11/11 (100)0/12 (0)28/53 (53)22/33 (67)0/10 (0)10/11 (91)
12/12 (100)21/53 (40)
1/33 (3)0/10 (0)0/11 (0)1/12 (8)28/53 (53)0/33 (0)0/10 (0)0/11 (0)0/12 (0)51/53 (96)22/33 (67)
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Antibody Panel for PDAC and Benign Epithelium

FIGURE 3. The classification tree proposed by the CART method. Four- (using p53, S100P, and claudin 4) (A) and 5-node (using p53, S100P,
claudin 4, and maspin) (B) classification trees were shown with prediction and misclassification for test data.

TABLE 3. Final Diagnosis and Cytological Diagnosis of EUS-FNA
Materials

use of only 1 marker may lead to false-positive results or a negative diagnosis. Therefore, to differentiate PDAC from benign pancreatic duct and contamination of the gastric/duodenal mucosa,
we investigated several markers and proposed the combination

Cytological Diagnosis
Final Diagnosis
Pancreatic ductal
adenocarcinoma (n = 53)
BE (n = 22)
Benign pancreatic duct (n = 14)
Gastric mucosa (n = 5)
Duodenal mucosa (n = 3)

Benign Atypical Suspicious Malignant
0

1

4

48

22
14
5
3

0
0
0
0

0
0
0
0

0
0
0
0

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TABLE 4. Diagnostic Value of the 4-Node Classification Tree in
TMAs and EUS-FNA Samples

Sensitivity (%)
Specificity (%)

TMAs

EUS-FNA

96.2
100

100
95.5

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TABLE 5. Diagnostic Accuracies of Cytology, Cell Blocks, andImmunocytochemistry, Alone or in Combination, in the
Detection of Pancreatic Ductal Adenocarcinoma
Sensitivity (%)

Specificity (%)

90.6%
73.6%
96.2%
100.0%

100.0%
100.0%
100.0%
100.0%

Cytology
Cell block
Cytology + cell block
Cytology + cell block + 4-nodeclassification treeof useful markers and a classification tree for diagnosing PDAC.
Use of CART methods seems a reasonable way for constructing
an optimized immunostaining panel. However, final diagnosis
should be made by overall assessment because in this study, there
were a couple of misclassified cases by CART methods alone.
Our immunostaining results from TMA sections indicatedthat p53 had the ability to distinguish PDAC from all samples contaminated by BE; however, its sensitivity and specificity were
53% and 100% by itself. The other markers did not differentiate
PDAC from BE when used alone. Therefore, we derived a classification tree for diagnosing PDAC using CART software on thebasis of immunohistochemical results from TMAs. As shown in

TABLE 6. p53 Heterogeneity on Large Sections (p53 Positivity, %)Spot #
Pancreatic ductCase 1Case 2
Case 3
Case 4
Case 5Gastric mucosa
Case 1Case 2
Case 3
Case 4
Case 5
Duodenal mucosa
Case 1Case 2
Case 3
Case 4
Case 5

1

2

3

4

5

2.99
0.45
2.56
0.22
0.00

3.47
2.37
1.22
0.00
0.00

0.00
0.85
0.55
0.00
0.00

3.13
0.05
0.03
1.39
0.00

0.32
0.00
0.20
0.00
0.87

2.81
0.00
0.09
0.18
0.12

2.68
0.00
0.13
0.02
0.45

0.20
0.00
0.00
0.06
0.98

0.05
0.00
0.00
0.16
0.19

0.69
0.00
0.00
0.08
0.18

0
0.27
1.14
0.21
0.00

1.42
0.00
0.73
0.96
0.18

0.93
0.00
2.00
1.32
2.98

0.50
0.25
1.83
1.43
2.15

1.03
0.09
0.00
0.92
0.32

FIGURE 4. The PDAC diagnosed as atypical on cytology ([A] Papanicolaou 200; [B] Papanicolaou 400). The cluster of adenocarcinoma
cells on a cell block ([C] HE 400) was positive for p53 ([D] immunostain 400). Resected pancreas tumor showing moderately to poorly
differentiated PDAC ([E] HE 40). High-power magnification of (E) ([F] HE 400).

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Pancreas • Volume 46, Number 4, April 2017

Figure 3, 4- and 5-node classification trees were provided bya CART analysis, and we also investigated the error rates of the
2 classification trees. Because the 5-node classification tree had
1 misclassification case in benign, we set the 4-node classification
tree as the best minimal combination of antibodies for diagnosing
PDAC. One interesting result of the present study was that the cutoff point for detecting p53 in PDAC was 5%. The cutoff point for
p53 based on an ROC analysis was 5%, which was lower than thatof a previous study on EUS-FNA that used p53 as a marker.8 The
lower positivity of p53 as evidence of PDAC may be related topremature senescence.
Premature senescence in response to abnormal mitogenic
signaling is a mechanism underlying tumor suppression. Serrano
et al20 showed that the expression of oncogenic ras in primary human or rodent cells resulted in permanent G1 arrest, and this was
accompanied by the accumulation of p53 and p16. They also demonstrated that senescence induced by oncogenic ras was indistinguishable from cellular senescence.20 The KRAS is mutated inmost cases of PDAC.21 In the progression of oncogenic KRASinduced carcinogenesis in the pancreas, the activity of the tumor
suppressor p53 is promoted in oncogenic-induced senescence inwhich p53 is genotypically the wild type.22
In the present study, the expression of p53 allowed for the detection of the mutant and wild-type forms of the p53 protein.
However, the relationship between p53 immunohistochemistry
and the p53 mutation status has been controversial.23 The immunohistochemical overexpression of p53 may closely correlate withthe p53 mutation. The lower positivity of p53 may reflect the accumulation of wild-type p53 interpreted as premature senescence.
In this case, the normally low level of p53 is elevated by cellularstress such as an oncogenic insult.20 Therefore, the cutoff pointof 5% for p53 in the present study may be valid for distinguishing
PDAC from BE.
Furthermore, p53 heterogeneity is an important issue when
adopting a lower cutoff point of p53 in the diagnosis of PDAC
in EUS-FNA specimens because p53 may not be expressed in a
fraction of the tissue. Because we only punched out 2 tissue coresfrom each block, TMAs contained only a limited amount of tissue.
To assess the difference in p53 positivity in BE (benign pancreatic,
gastric, and duodenal mucosae) between resected specimens andTMAs, we analyzed the p53 positivity of 5 spots from eachresected specimen. Our results revealed that all cases of p53 positivity were less than 5%. This result was the same as that of
TMAs and indicated that cases with more than 5% positivity for
p53 are regarded as PDAC and also that a lower cutoff point
may be used for EUS-FNA samples.
Among the 53 PDAC cases in the present study, there wasonly one atypical case on cytology (Fig. 4). This case was diagnosed as moderately to poorly differentiated PDAC by a histological diagnosis of the resected pancreas. In cytological smears, thiscase was confused with the gastrointestinal epithelium because
clusters of neoplastic cells showed flat sheets, and there was no remarkable cellular atypia. The cell block preparation contained
only 1 cluster of atypical cells, that is, positive staining for p53,
and may be diagnosed as PDAC using an HE-stained cell blockpreparation and immunocytochemistry.
Although we investigated useful markers for diagnosing
PDAC, IPMNs are also difficult to distinguish from a nonneoplastic
gastric mucinous epithelium based on cytological features alone.24
In Western countries, EUS-FNA is preferable for histologicaland/or cytological diagnoses of IPMNs. Data to support the utilityof EUS-FNA in pancreatic cystic neoplasms are limited, and thepositive predictive value of an FNA diagnosis of IPMN and thesensitivity of FNA cytology for IPMNs is not yet established.
Sedlack et al25 investigated 18 cases and revealed that whereas© 2017 Wolters Kluwer Health, Inc. All rights reserved.

Antibody Panel for PDAC and Benign Epithelium

specificity was high (100%), the sensitivity of cytology was only
27% for diagnosing IPMNs. In a recent single-center study of
141 cysts, cytology findings were highly specific (51/53, 96%),
whereas sensitivity was moderate (61/141, 43%).26 In Japan, endoscopic retrograde cholangiopancreatography is recommended
for a cytological diagnosis of IPMNs instead of EUS-FNA becauseof the risk of the dissemination of tumor cells or pseudomyxoma
peritonei after EUS-FNA. Therefore, we did not investigate IPMN
cases in this study. However, if an EUS-FNA diagnosis of IPMNs
is required to improve the poor sensitivity associated with diagnosing IPMN by EUS-FNA, further studies on immunohistochemical methods to distinguish PDAC from benign gastricmucosa are needed.
In summary, to the best of our knowledge, we are the first toreport a useful immunostaining panel for distinguishing PDAC
from all contaminated BE in the English-language literature.
An accurate diagnosis of PDAC on EUS-FNA cell blocks issometimes difficult because of the limited amount of tissue, particularly in cases of a small amount of tissue and well-differentiatedPDAC. Contamination of gastric/duodenal epithelium is a diagnostic pitfall in the diagnosis of PDAC. In this case, the classification tree using 3 antibodies (p53, S100P, and claudin 4) proposed
herein seems to successfully distinguish PDAC from the accompanying contaminated BE in EUS-FNA samples.
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Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.