Since decades, pathologists extensively consult with fellow pathologists to collect expert opinions on difficult cases. This is due to the fact that pathology is dealing with an area of diagnostics that is extremely variable. General pathologists are able to diagnose virtually any disease, but in rare or complex cases it is common practice to consult a (pathology) expert. It is also true, that many pathology labs have developed particular expertise in certain subspecialties and receive consult cases predominantly for these specific indications. 

Coming from the digital pathology (DP) domain I was certain, when learning about this extensive network of pathology consultation, that most if not all pathology labs use tele-pathology to ask for (remote) expert opinions. For me, the many advantages were obvious when comparing to the alternative, the traditional, non-tele way: Shipping blocks or slides takes much longer and has risks (of losing or damaging the material) - and time plus risk reduction are two important matters for any lab. 

I had to learn, however, that only few pathologists are as excited as me about performing tele-pathology for expert consultation, due to various reasons:


Traditionally, pathologists either share a glass slide or the tissue block when asking for remote consultation. Since the glass slide is the fundamental source of evidence for the diagnosis, pathologists are quite reluctant to send it, so sending the block is, if possible, the preferred way. Sending the block has the advantage that the consulting pathology lab can apply its own stains. But generating duplicate sections also reduces the amount of valuable tissue and is only possible if there is enough material within the tissue block in the first place (which is usually not the case for e.g. lung biopsies). If the block rather than the slide is requested, however, tele-pathology solutions cannot be used. 


To perform tele-consultation a lab has to massively invest into a DP solution. Considering the entirety of hardware, software, and effort of staff to establish and introduce the solution, costs can easily exceed 1 million USD, which takes some years to amortize. Especially the small and mid-size labs, where the demand for (remote) expert opinion is largest, cannot afford the spending for a fully fledged DP solution. However, more and more labs are taking the step to go digital, especially after the first DP system was approved by the FDA for primary diagnosis earlier this year. But for tele-consultation, this is only half the battle. The other end needs to run a DP system, or at least a software for viewing, commenting, and annotating virtual slides, too. Most DP scanner vendors provide such a software for free, but they are usually limited to one specific virtual slide format. Experts who consult for various labs running different DP solutions need to switch between various applications, which adds extra burdens to pathologist and IT staff.


Once both, local and remote DP systems are up and running there is the need to transfer virtual slides. One would think that sharing images is easily done via the web. Not so in the world of digital pathology: A virtual slide contains much data and is - depending on the format - often distributed throughout several files. Uploading such files or file sets is time-consuming and moaning sounds from the IT department can surely be expected.


At this point I asked the question if the ever increasing speed of internet connections would overcome this challenge in the future. Assuming the average size of a virtual slide scanned on 40x resolution is 850 Megabytes1and an upload speed of 10 MBits/second, the transfer of one virtual slides takes a bit more than 10 minutes. For tele-consultation of a complicated case one would usually transfer about 5 virtual slides, keeping the transfer time below 1 hour, which is quite long whatsoever. If the resolution of the scans are kept to 20x, however, the transfer time can be cut down to 15 minutes for the entire case, so: is bandwidth and upload times, together with storage costs decreasing year over year, really still a barrier?


Transferring pathology data via the web requires several safety criteria to be met. Even though many pathologists I talked to use non-HIPAA compliant file sharing apps together with email correspondence or even share their images within social networks, a professional tele-consultation system should guarantee Protected Health Information (PHI) to be secured. Even though a histology image per se is not considered PHI, the metadata stored within a virtual slide or the pathologist’s descriptions that are necessary information for the consulting expert quickly make it PHI. Using non-HIPAA compliant sharing systems require the pathologist to carefully decide what information is shared and what information is kept private, a fact why tele-consultation is often discarded. 


Finally, one of the most important limiting factors why tele-pathology for expert consulting is only hesitantly adopted by the pathology community, is the ease to use these systems: Pathologists have virtually no extra-time and cannot afford to invest hours in learning complicated user interfaces. More importantly, the sharing of a case with a colleague should not require many steps and involve various people: If a pathologist cannot share a case with a colleague with only a few clicks from their work desk, tele-consultation will not happen. One of the easiest ways to do tele-consultation is to use screen-sharing tools where the asking pathologist shares a screen (displaying the case and its virtual slides) and the consulting pathologist can remotely control the shared screen. These tools are, once installed, very intuitive and easy to use, and they just require one end to be equipped with a DP solution. But they lack one fundamental functionality, which is the possibility for asynchronous communication: Screen sharing requires both pathologists to sit in front of their workstation at the same time, which is simply impossible for many consultation use cases. 

Despite all these reasons, there are many pathologists already using tele-pathology for consultation, even across national borders. But the majority of consultation cases are still done the traditional way, by sending blocks and glass slides via postal mail. 


So what would a tele-consultation system look like that has the potential to a broad acceptance and usage?



It must be easy to access: Given a device connected to the internet you should be able to immediately run the system. That is, no installation, no or very simple interfaces to other software systems of the lab, no storage requirements, and ideally running on mobile and stationary devices alike. 

It must be easy to use: Sharing of virtual slides and communication must be accompanied by an extremely easy set-up that only focuses on this particular use case: upload, annotate, invite, and comment with a few clicks. 

It must be easy to afford: Optimally, such a system should be provided for free or for a minimum fee to account for the very limited reimbursement levels of pathologists’ work in many countries. 

It must be fast: As discussed, the transfer of virtual slides is taking time. If this time cannot be spent, there should be other options for online collaboration: Support the sharing of smaller fields of view, or live streams of camera microscopes to speed things up if need be. 

It must be secure: Data safety, security, and secure communication channels should allow pathologists to share any information they are willing to. If a system is compliant to the HIPAA, US pathologists would be able to share even PHI. In other countries, where laws are less clear or requirements for data security are higher, these systems should adapt, or at least provide tools for a thorough anonymization of patient data before sharing cases. 

It must be truly vendor neutral: Support of all data formats is a must - no assumption can be made on the underlying hardware that produces the images or a possible standardization of virtual slide formats in the future. Moreover, labs in non-industrial countries cannot afford a DP solution but create digital images with their camera microscopes. For them, tele-consultation should be made possible, too. 


Sounds quite doable, no rocket science to be mastered. So do neither software nor hardware providers see a business case behind it? True for some, but surely not all. Or have I forgotten a fundamental requirement? 

Some might bring in the issue of the image quality that differs between slide scanners. This was quite a problem a few years ago, but nowadays most slide scanners produce good and consistent image quality within a reasonable amount of time.

Many will argue that such a system must be optimally integrated into the pathology workflow and software eco-system, which ultimately boils down to interfacing with existing laboratory/hospital information systems (L/HIS) as well as image management systems (IMS). And this is, from a technical perspective, challenging indeed: There are more than a hundred different LIS providers operating in developed countries and, due to lack of standardization, there are at least as many IMS as there are scanner providers. Creating interfaces to the existing IT infrastructure and deploying these systems into pathology labs takes time, costs money, and involves more stakeholders into the process, e.g. lab managers and IT staff. This inevitably increases the costs for such a solution while decreasing flexibility and versatility. At this point, it is important to balance the benefits of a full integration with the costs: Is it really necessary for tele-consultation to directly access all the information stored in the LIS? Or is the effort it takes to copy the relevant information from the LIS into the tele-pathology system acceptable if this system can be available (almost) for free? 

In either case, the patient benefits from a consultation solution based on tele-pathology: The quality of the diagnosis is likely to increase while turnaround times will decrease. And that’s the good news.

1 We have averaged the size of > 15 000 virtual slides with formats from most slide scanner manufacturers, a resolution of 40x, and commonly used compression methods.