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. 52920) 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 93-100% 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 Pantanowitz L, Sinard JH, Henricks WH, Fatheree LA, Carter AB, Contis L, Beckwith BA, Evans AJ, Lal A, Parwani AV. “Validating whole slide imaging for diagnostic purposes in pathology: guideline from the College of American Pathologists Pathology and Laboratory Quality Center.” Arch Pathol Lab Med. 2013 Dec;137(12):1710   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