1. WSI-FS II: Validation of Squamous Cell Carcinoma Frozen Section Whole Slide Image Diagnosis in Surgical Pathology
Vamsi Parimi MD1; Ryba Dominika, Ewa Borys, MD1; Vijayalakshmi Ananthanarayanan, MD1; Swati Mehrotra, MD1; Xianzhong Ding, MD1; Maria M. Picken, MD PhD1; Dariusz Borys, MD1
1Department of Pathology, Loyola University Medical Center, Maywood, Illinois
INTRODUCTION
RESULTS
The utility of Whole Slide Imaging for Frozen Section (WSI-FS) slides is garnering increasing interest in anatomic pathology for primary diagnostic and consultation purposes. The College of American Pathologists (CAP) as part of its proficiency testing introduced WSI checklist (GEN ) to ensure the diagnostic performance of digitized slides on par to that of glass slides light microscopy for clinical use. In addition to technical issues, regulatory and validation requirements related to WSI-FS have yet to be adequately addressed. Our objective was to examine the results of a WSI-FS validation study performed using WSI clinical validation guidelines recently released by the CAP in a community/academic setting. Our study was the first to specifically looking at different tumor subtypes encountered in anatomic pathology frozen section diagnosis. The current study report results of validation of whole slide imaging for frozen section Squamous Cell Carcinoma (SCC) diagnosis to that of original glass slide (G-FS) interpretation. We have shared our previous WSI-FS I Adenocarcinoma study data at USCAP-2016
Among 246 specimens, 135 were positive for SCC, 104 negative for SCC and 7 lymph nodes positive for metastatic SCC.
FS specimens include slides with primary SCC neoplasms, margins of surgical resections and lymph nodes
The average scan times per slide was 2 minutes 30 seconds and average interpretation time per specimen was 2 minutes 30 seconds which included evaluation of superficial and deep frozen sections.
The wash-out interval was greater than 300 days.
Interobserver agreement between G-FS and WSI-FS ranged from 84-93%
Average false negative and false positive diagnosis on WSI-FS was 8.3% and 2.28% respectively
The sensitivity and specificity of WSI-FS diagnosis ranged from 85-96% and % respectively.
  The ratio of the odds of the WSI-FS being positive if the GS has a SCC relative to the odds of the WSI-FS being positive if the GS does not have the SCC (Diagnostic Odds Ratio) was 817 (average).
Inter-rater reliability between G-FS and WSI-FS; Cohen's Kappa Statistic ranged from 0.83 to 0.94 among the pathologists and demonstrated an overall excellent reliability for the observer agreement.
Pathologist Specialization
Bone/Soft tissue
Neuropathology
Genitourinary
HNT-1
HNT-2
Gastrointestinal
Total specimens (n=246)
G-FS
WSI-FS (A)
WSI-FS (B)
WSI-FS (C)
WSI-FS (D)
WSI-FS (E)
WSI-FS (F)
Positive for SCC
135
61%
61.30%
50.30%
58%
53%
57%
Negative for SCC
104
39%
38.70%
49.70%
42%
47%
43%
Suspicious for SCC
LN/ Mets Concordance 7
85%
80%
60%
100%
Overall Concordance
90% (208)
87% (193)
84% (176)
91% (185)
92% (162)
93% (234)
p value
<0.05
False +ve (Type I error)
4.70%
6.70% 0%
0.90%
1.40%
PPV
95%
96%
99%
False -ve (Type II error)
2.50%
6.60%
16.80%
8.90% 6%
NPV
97%
90%
83%
91%
Sensitivity (95% CI)
98.28
93.22
85.29
93.81
92.31
96.35
Specificity (%)
92.59
94.59
100
98.61
97.92
Positive likelihood ratio
13.26
17.24
N/A
67.54
46.248
Negative likelihood ratio
0.02
0.07
0.15
0.06
0.08
0.04
Diagnostic-OR (95%CI)
712
241
1075
1241
Cohen's Kappa Statistic
0.92
0.87
0.83
0.91
0.94
METHODS
A total of 108 FS SCC cases (246 specimens and 463 glass microscope slides) from random anatomic sites from 2013 and 2014 were identified (search word “squamous”) and scanned by Aperio CS2 slide scanner (Leica Biosystems, San Diego, CA, USA) with 20x/0.75NA Plan Apo objective lens
The digital images were visualized at 1916 × 1072 pixel resolution with eSlide Manager (Leica Biosystems) software.
In our study, 6 surgical pathologists specializing in neuropathology, head, neck & thorax pathology, bone and soft tissue pathology, genitourinary pathology and gastrointestinal pathology independently evaluated WSI-FS slides necessary to make a final diagnosis (presence or absence of SCC).
No clinical or prior diagnostic information (age, sex, clinical history, location, presence or absence of tumor) were provided to the pathologist in aiding diagnosis.
Pathologists reviewed the WSI-FS cases, without the knowledge of primary pathologist’s readout on G-FS.
CONCLUSION
We established diagnostic concordance between digital and glass slides by CAP-PLQC recommended guidelines for the SCC tumor subtype in an institutional laboratory system at ×20 magnification among pathologists sub-specialized in surgical pathology.
This study was the first to specifically evaluate WSI-FS diagnosis of SCC. 
REFERENCES
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  Têtu B, Evans A. Canadian licensure for the use of digital pathology for routine diagnoses: one more step toward a new era of pathology practice without borders. Arch Pathol Lab Med. 2014 Mar;138(3):302-4