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Why is digital pathology in cytopathology lagging behind surgical pathology?

2017; Wiley; Volume: 125; Issue: 7 Linguagem: Inglês

10.1002/cncy.21855

1934-6638

Matthew G. Hanna, Liron Pantanowitz,

Cell Image Analysis Techniques

Cancer CytopathologyVolume 125, Issue 7 p. 519-520 Cytopathology Help DeskFree Access Why is digital pathology in cytopathology lagging behind surgical pathology? Matthew G. Hanna MD, Matthew G. Hanna MD orcid.org/0000-0002-7536-1746 Search for more papers by this authorLiron Pantanowitz MD, Liron Pantanowitz MD orcid.org/0000-0001-8182-5503 Search for more papers by this author Matthew G. Hanna MD, Matthew G. Hanna MD orcid.org/0000-0002-7536-1746 Search for more papers by this authorLiron Pantanowitz MD, Liron Pantanowitz MD orcid.org/0000-0001-8182-5503 Search for more papers by this author First published: 05 May 2017 https://doi.org/10.1002/cncy.21855Citations: 17AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Digital pathology has matured substantially since commercial whole-slide imaging (WSI) solutions first were introduced approximately 16 years ago. There have since been significant advances in imaging and scanner technology, success with various applications such as telepathology, progress made toward obtaining regulatory approval to use WSI for primary diagnosis, and the development of guidelines that have helped to standardize clinical practice and promote the adoption of digital imaging in pathology. Recently, only a few pathology laboratories have claimed that they have actually started going "fully digital." To date, this includes laboratories in Sweden, the Netherlands, Spain, and Singapore.1-3 However, much of this effort has been devoted to surgical pathology. Cytopathology teleconsultation using WSI also has not been as pervasive as surgical telepathology.4 The question remains: why is WSI in cytopathology lagging behind? Compared with surgical pathology, to our knowledge there is limited literature regarding WSI in cytopathology.5, 6 The majority of cytology articles to date have been devoted to real-time dynamic digital microscopy for telecytology. Several published validation studies already have proven that diagnostic review of surgical pathology cases by WSI is not inferior to microscope slide review.7, 8 Conversely, in a study that examined diagnostic concordance between glass and digital cytology slides, the investigators demonstrated that glass slides were more accurate and faster.9 There are several barriers that still need to be overcome in order for digital pathology to become more widely used. These include, among others, the cost of this technology, regulatory approval for the diagnostic use of WSI, and standardization of image file format among vendors. However, these obstacles apply to all areas of pathology, including surgical pathology. There also are several reasons more unique to cytopathology that may explain why WSI has not caught on as quickly in this field. They include the nature of cytology samples themselves, image acquisition challenges, and differences in clinical workflow. Let us consider each of these potential impediments. Cytopathology includes a variety of specimen types, including Papanicolaou (Pap) tests, fine-needle aspirations, and exfoliative samples. These typically are composed of single cells, and sometimes cell groups without substantial tissue architecture. Also, there are often a variety of preparations that need to be examined, including direct smears, liquid-based cytology, and cell blocks. This diversity poses challenges for routine, high-volume digitization. Moreover, whereas ×20 magnification whole-slide scanning may suffice for the majority of surgical pathology slides, higher resolution (eg, ×40 scanning) is desirable for cytology slides to reliably interpret fine cytological details. Unfortunately, scanning at ×40 magnification takes longer and produces larger files. Next, the accurate evaluation of a digital cytology slide requires that all of the cells present are viewable and in focus. However, this may not always be possible when cytology slides have thick smears and/or specimens contain 3-dimensional cell groups. Even with liquid-based samples in which monolayers are generated, cell clumping still occurs.10 With the use of flat tissue sections in surgical pathology, there are fewer topographic variations, with the exception of occasional tissue folds. Hence, it is more important to be able to observe cytologic material in both horizontal (x and y) and vertical (z) axes. For WSI, the need for focusing can be addressed by z-axis scanning.11, 12 This involves scanning a glass slide at different focal planes along the z-axis and stacking the generated images atop each other to produce a final composite (z-stack) multiplane image. Such z-stacks allow the cytologist to "focus up and down" the different planes. Today, several WSI scanners offer z-stacking capability. However, z-scanning takes longer and produces large digital files. Data sets with large files may result in slow loading, pixilation, and freezing of images, especially if computers and networks are limited, which may result in observer frustration. In an attempt to overcome this problem and not just wait for WSI technology to improve, some authors have proposed making and scanning only cell blocks for Pap tests instead of processing and then imaging liquid-based cytology preparations for cervical cancer screening.13 Finally, it is not uncommon to receive cytology specimens that contain only scarce abnormal cells (eg, so-called "litigation" cells in Pap tests) hidden among thousands of normal cells or buried somewhere within background material. This differs from surgical pathology, in which the majority of appropriately targeted biopsies or resected specimens contain ample lesional tissue that is relatively easy to detect. This means that in nearly all cases, every cytology slide needs to be entirely and systematically screened with close scrutiny, usually at varying magnifications. Current WSI viewers and workstations (eg, using a computer mouse) are not ideal for manually performing the taxing task of screening cytology slides, especially for high-volume work. The aforementioned attributes help to explain why the use of WSI in cytopathology is more problematic than in surgical pathology. We are hopeful that soon our digital pathology vendors will offer us more suitable solutions that can be used for primary diagnosis in cytopathology. Further technologic advances that support the faster creation of multiplane WSIs that are easier to manipulate, manage, and analyze will help to drive the widespread use of WSI in cytopathology. FUNDING SUPPORT No specific funding was disclosed. CONFLICT OF INTEREST DISCLOSURES Liron Pantanowitz has acted as a paid consultant for Hamamatsu and Hologic for work performed outside of the current study. Biographies Dr. Hanna is a clinical instructor of pathology informatics at the University of Pittsburgh. He completed his residency training at the Mount Sinai Hospital in New York City and currently is a pathology informatics fellow at the University of Pittsburgh Medical Center. Dr. Hanna serves as a junior editor of the Journal of Pathology Informatics. He has strong interests in pathology and clinical informatics, as well as women's health pathology. Dr. Pantanowitz is a professor of pathology and of biomedical informatics at the University of Pittsburgh. He is the director of the Pathology Informatics Division and director of the Pathology Informatics Fellowship at the University of Pittsburgh Medical Center. He also is the director of cytopathology at the University of Pittsburgh Medical Center Shadyside. Dr. Pantanowitz is an editor-in-chief of the Journal of Pathology Informatics and also is a member of the board of directors for the Digital Pathology Association and the executive board of the American Society of Cytopathology. He serves as a council member for the Association for Pathology Informatics, and is a member of the College of American Pathologists Digital Pathology Committee. He has widely published in the field of pathology informatics, including digital imaging and its application to pathology. REFERENCES 1 Thorstenson S, Molin J, Lundstrom C. Implementation of large-scale routine diagnostics using whole slide imaging in Sweden: digital pathology experiences 2006-2013. J Pathol Inform. 2014; 5: 14. 2 Stathonikos N, Veta M, Huisman A, van Diest PJ. Going fully digital: perspective of a Dutch academic pathology lab. J Pathol Inform. 2013; 4: 15. 3 Cheng CL, Azhar R, Sng SH, et al. Enabling digital pathology in the diagnostic setting: navigating through the implementation journey in an academic medical centre. J Clin Pathol. 2016; 69: 784- 792. 4 Zhao C, Wu T, Ding X, et al. International telepathology consultation: three years of experience between the University of Pittsburgh Medical Center and KingMed Diagnostics in China. J Pathol Inform. 2015; 6: 63. 5 Amin M, Parwani AV, Pantanowitz L. Digital imaging. In: L Pantanowitz, AV Parwani, eds. Practical Informatics for Cytopathology. New York: Springer; 2014: 129- 145. 6 El-Garby EA, Parwani AV, Pantanowitz L. Whole slide imaging: widening the scope of cytopathology. Diagn Histopathol. 2014; 20: 456- 461. 7 Bauer TW, Schoenfield L, Slaw RJ, Yerian L, Sun Z, Henricks WH. Validation of whole slide imaging for primary diagnosis in surgical pathology. Arch Pathol Lab Med. 2013; 137: 518- 524. 8 Snead DR, Tsang YW, Meskiri A, et al. Validation of digital pathology imaging for primary histopathological diagnosis. Histopathology. 2016; 68: 1063- 1072. 9 House JC, Henderson-Jackson EB, Johnson JO, et al. Diagnostic digital cytopathology: are we ready yet? J Pathol Inform. 2013; 4: 28. 10 Fan Y, Bradley AP. A method for quantitative analysis of clump thickness in cervical cytology slides. Micron. 2016; 80: 73- 82. 11 Pantanowitz L, Parwani AV, Khalbuss WE. Digital imaging for cytopathology: are we there yet? Cytopathology. 2011; 22: 73- 74. 12 Donnelly AD, Mukherjee MS, Lyden ER, et al. Optimal z-axis scanning parameters for gynecologic cytology specimens. J Pathol Inform. 2013; 4: 38. 13 Tawfik O, Davis M, Dillon S, et al. Whole-slide imaging of Pap cellblock preparations is a potentially valid screening method. Acta Cytol. 2015; 59: 187- 200. Citing Literature Volume125, Issue7July 2017Pages 519-520 ReferencesRelatedInformation