From Magic to Molecules: The Intelligent Microscope
Almost 200 years ago a new technology, the microscope, revolutionized the way in which medicine was practiced, resulting in the invention of Surgical Pathology as a discipline. Today the advent of molecular testing of tissue sections, coupled with digital whole slide imaging and analysis using an ‘intelligent microscope,’ is bringing about changes in Pathology of even greater magnitude, that will again ‘re-invent’ how we practice Pathology.
- Describe in outline Companion Diagnostics, how they are developed, approved and used in pathology.
- Understand the advantages and limitations of on-slide evaluation and scoring.
- Evaluate the potential role and utilization of artificial intelligence in assisting the pathologist with histopathologic diagnosis.
There are some basic objectives for today, really to talk a little bit about companion diagnostics and to understand some of the limitations in how we assess them and perhaps to look at the future role of artificial intelligence as to how it may assist us. This, of course, is a personal view, and the opinions I present are entirely my own for good or for ill. On reflection, pathology has exploited technology. We've been good at that, but really I believe that technology has shaped pathology and who we are and what we are. One hundred and eighty years ago, I think the microscope invented the pathologist, not the other way around, and I think that today the digital microscope or the intelligent microscope is about to reinvent all of us.
I was fortunate over the past couple of years to work with Jan van den Tweel and Jiang Gu in a book called From Magic to Molecules, which involved 30 pathologists from around the world who reviewed their various disciplines as to how pathology and the understanding of disease had evolved. In every instance, when we reflected on that book it was clear that the whole process had been technology driven. That applies to microbiology, of course, where the microscope was introduced two or three hundred years ago and really led to precision diagnosis in infectious disease through the evolution of antibiotics.
Within anatomic pathology, things have been a little bit different, but, again, the microscope has been central to the whole process. The first leukemia was described by Bennet in Edinburgh in about 1840, and since then there have been increasing entities recognized by microscopy. There is a similar and dramatic shift towards precision diagnosis and precision treatment, and it's changing the face of pathology through companion diagnostics. This era really started very abruptly on September 25, 1998—that's 20 years ago almost—when the FDA wrote to DAKO, as it was then, to approve the HercepTest. Digital pathology has since evolved dramatically. It really wasn't available at the time that the HercepTest was introduced, and digital pathology itself was approved by the FDA for primary diagnosis just last year. I'll refer to that again a little later because the impact of that approval is potentially very large.
The early days
Now, just on reflection then, prior to the microscope there was morbid anatomy, but by about 1850 that began to change. John Hunter was one of the people that changed it. He was a surgeon in London, in fact. He's a Scotsman, but he was a surgeon in London. In his career he performed more than 10,000 autopsies, and he made 13,000 specimens in jars, if you will. For those of you that do visit London, there's a wonderful collection of many of his specimens in the Royal College of Surgeons Museum in London. His original museum you can see there on the right-hand side was lost mainly during the war, and many specimens were destroyed but there are still many at the Royal College of Surgeons.
So why did things change in the 1840s and 50s? Well, we have to not really give credit but attribute the change to two individuals named Burke and Hare who were providing bodies to a surgeon in Edinburgh whose name was John Knox, and he was paying them for the bodies about seven pounds and ten schillings of gold. These were for the education of medical students. The problem is he needed more bodies than were available by natural means, so Burke and Hare sort of accelerated the process a little bit and eventually were convicted for murdering 16 people whose bodies were sold to Knox. Hare plea bargained, and he disappeared. He was thought to have died of tuberculosis in London a few years later, but Burke was executed and he was publicly dissected in Edinburgh.
This is the execution and confession of Burke, and he was publicly dissected by the Professor of Pathology in Edinburgh at that time who was known as Monro Tertius because his father had been professor before him and his grandfather before him. For a hundred plus years the Munro's were the professors of pathology in Edinburgh. Now, all of this produced a dramatic change because it changed the law in the United Kingdom and eventually in Europe and around the world that made dissection legal for medical purposes because prior to then dissecting a body was illegal. That was the - - pathology up to about 1850.
The Microscope in Pathology
Now, as I mentioned earlier, the microscope had been around since 1700, but it took about 140 years until 1840 before the microscope was widely used in pathology. There were reasons for that. Adoption was slow because resolution was poor. Quality of the instruments was poor, and the cost was very high. A man called Joseph Lister, who was actually Lord Lister's son, the man who invented antisepsis, Lord Lister's father rather, he introduced improved lens grinding methods. He actually wrote a paper with Thomas Hodgkin called Observations of the Blood in Animal Tissues Using a Microscope. Interestingly, when Hodgkin published his paper five years later on the absorbent glands of the spleen, that's the paper that essentially introduced Hodgkin's disease to the world, Hodgkin did not use the microscope because he felt it still was not generally useful.
It was another decade or two before the first pathology microscopy texts appeared. Virchow's book, of course, is the more famous of the two, Cellular-Pathologie, but the book by Sir James Paget was actually titled Lectures in Surgical Pathology. Our discipline of anatomic or surgical pathology as we know it today with the microscope began about 1850. This led to a tremendous explosion of pathology. In fact, anatomic pathologists, surgical pathologists did not exist prior to 1850 because the technology had not invented them. It's actually been the age of the microscope, and for 150 years that's how we diagnose cancer and everything else. This was really image analysis by mind and by microscope. The names of the people on this slide here almost all have stains attached to them, Weigert, Aschoff, Cajal, Virchow, and I put Bob Lukes on the slide because I was privileged to work with him for 30 years. He was a wonderful microscopist.
So all of that led to about 1900 when the technology of pathology really was the microscope, the formalin paraffin section, and a set of histochemical stains. If you notice, all of those stains, the basic biologic stains that we use today all were invented and introduced in conjunction with the microscope. Again, new technology in the period from about 1850 to 1900. So in 1900 then the legacy was the microscope and the H&E, and, interestingly, by 2018 not much had changed. But things are already beginning to change.
Our legacy then with the formalin paraffin section was forming the standard method of processing tissue. That was introduced by Blum and Blum, father and son, in 1893. That's really still the standard. There have been attempts to introduce other fixatives, but none have replaced formalin or displaced formalin. Secondly, our legacy was that morphologic diagnosis is by H&E. We have to recognize that that is subjective. Many clinicians have been concerned that morphologic diagnosis is subjective. If we just look at these six cases, for example, the diagnosis is to a degree a matter of opinion. The more experience one had in the field, the one more one's opinion is respected and the more likely it is to be correct in relationship to whatever the consensus diagnosis is.
A number of clinicians had been a little disrespectful and perhaps rightly. This is Marcel Bessis in 1980 at a meeting where we were talking about anatomic pathology. He was a hematologist, and he said well it's a level of science. It's about the same level of science as collecting butterflies. In retrospect, he was correct. It's an opinion as to whether a butterfly is this or that. There's not much in the literature about the subjectivity of pathology, and perhaps that's because we don't like to write too much about our deficiencies.
Here's one manuscript from about 20 years ago. These were soft tissue tumors. They looked at 89 lesions, four different pathologists independently, and they each scored them. So 89 multiplied by four gives 356 calls. These pathologists looked at these without a clinical history, and of those 356 calls 172 were malignant. There was then a washout period to forget the cases, and they re-looked at them, but then they were given the clinical history and suddenly 227 were malignant. Same glass slide, same morphology, same everything, but it just shows the subjectivity of the diagnostic process on H&E.
There was a seminal paper published in 1985 by Kevin Gatter, who happened to have been a student in my lab back in Oxford in 1974 when we were first doing immunohistochemistry. Kevin did a very brave thing. He was then a junior faculty person at Oxford, and he took 120 consecutive routine cases that had been classified as anaplastic malignancy or as anaplastic carcinoma or lymphoma. So he had 120 of those. Twenty-four were unclassified. Forty-three were carcinomas. Fifty-three were lymphomas. He did very basic immunohistochemistry on those. With that basic immunohistochemistry, just staining for keratin and leukocyte common antigen, which was all he had available in 1985, he found that of those classified as carcinoma 43 cases—in fact, 29 were lymphomas. So over half of all these diagnoses were, in fact, wrong.
New Independent Techniques
This was the beginnings of recognition that the morphology could be improved by having independent techniques to give a more definitive cellular recognition. Now, over four decades all of this has accumulated, and the role of pathology has changed. We were pretty excited at USC ten years ago if we could persuade our residents to identify four morphologic types of lung cancer—small cell, non-small cell, adeno, squamous, and large cell not otherwise specified. It was hard work getting to do that. We added some immunohistochemistry. They got better at it, and now if we do that and send that result to the clinician they're not happy. What they want to know now are what the subtypes of adenocarcinoma are not in relationship to morphology but in relation to the abnormal proteins that are expressed, particularly those proteins for which they have in their toolbox a targeted therapeutic, a targeted therapeutic for