To the Editor.—I read with interest the article by Evans et al1 outlining barriers and possible approaches to implementing whole slide imaging (WSI) into clinical practice. Although this technology has been widely accepted for teaching and research, there are obstacles—real and perceived—for application to patient care. Ironically, light microscopy, the current gold standard, experienced numerous difficulties entering diagnostics. Although some versions of the microscope were available by the early 1600s, applications in pathology waited 250 years. There were 8 reasons for the delay, including price, poor optics, and distrust (ie, “the fear of studying optical artifacts, of chasing shadows instead of dealing with realities”).2(p274) Even cell theory/cancer biology pioneer Johannes Müller was adamant that, although useful for cancer research, the microscope should never be used diagnostically.3 Alfred Stille, in his textbook Elements of General Pathology, wrote in 1848:
“The use of the microscope in pathological investigations is an art so difficult, that none but those who have especially, and for a long time, cultivated it, can depend upon the correctness of their observations, or estimate justly the phenomena they witness. On this account it can never become … of habitual employment in ordinary practice, even were the points of pathology which it is capable of elucidating much more numerous than they really are ... It still must be admitted that the value of the microscope is less questionable as a means of detecting crystallizable product in the urine, when they exist there in such small quantities as to elude chemical analysis….”4(p198)
Because light microscopy was more readily accepted as a new technology in clinical pathology, it followed this path of least resistance into diagnostics.3 In 1853, Baltimore pathologist Francis Donaldson tried to debunk mistrust of light microscopy in anatomic pathology:
“If those who think there is no reliance to be placed on appearances in the field of the microscope would take any crystal, such as that of the beautiful octohedra [sic] of the oxalate of lime visible already to the naked eye, and magnify it by degrees, they would see that, no matter what the power of the glass used, it possesses the same number of sides, angles, &c. [etc]; the only difference being that the minute details, not visible before, would be brought out. They ought to remember that no matter how high the magnifying power of a lens, it cannot render visible things which do not really exist—it cannot create.”5(p45)
Undoubtedly, the diagnostic use of WSI will prove to be as safe as light microscopy, a technology that never needed regulatory approval by the US Food and Drug Administration, or faced any of the other WSI barriers.1(Table1) Early adaptors of WSI are at the forefront of exploiting a useful diagnostic tool just like Donaldson more than 160 years ago. Such innovation must advance through “baby steps,” following pathways of least resistance. Evans et al1 should be congratulated on outlining a well-conceived, stepwise path toward implementation of WSI into areas of pathology clinical practice. Once enough early adopters have followed those pathways, other, more spacious, avenues will open.
Departments of Pathology & Laboratory Medicine and Paediatrics, University of Calgary/Calgary Laboratory Services, Alberta Children's Hospital, Calgary, Alberta, Canada
Accepted for publication July 21, 2017.
The author has no relevant financial interest in the products or companies described in this article.