Pathology, a path well worn


Recently I attended a meeting on breast cancer and was somewhat taken aback to hear a clinical oncologist lambast pathologists as not having advanced their discipline in tandem with progresses in biomedical research. I was surprised on two fronts: firstly that the oncologist was not taken to task by the medical pathologists in the audience; and secondly that such incorrect assumptions were not challenged by those same pathologists.

While the origins of microscopic pathology have been attributed to Rudolf Virchow (19th century), the process of dissecting bodies (the post-mortem examination) had its origins over 2000 years earlier. The workings of the modern pathologist remain focussed on detailed post-mortem examinations and the evaluations of the “blue and pink” (haematoxylin and eosin) stained slides. To suggest that if such procedures have not changed, then we have not progressed, is to suggest that clinical medicine has also not advanced as clinicians still use the “tool” of the clinical examination. Of course one would argue that clinical medicine has advanced as there is the constant advancement in imaging modalities and new ante-mortem molecular/biochemical tests. However in the same vein, the pathologist can argue that there are ongoing advances in histopathology in the allied areas of immunohistochemistry, in-situ hybridisation, laser microdissection and telepathology. The important point to note in all of this is that these advances are not designed to replace the clinician or pathologist but continually require their age-old expertise to endorse and validate them. Nothing can replace a quality clinical or pathological assessment, but supported by ante-mortem and post-mortem testing these evaluations have a much more robust end-result, providing a more accurate encompassing diagnosis of greater benefit to the patient and thereby educating all involved in the diagnostic process.

The detailed study by Dank and others (2012) from the University of California at Davis (this issue), drives home the above points highlighting the continual value that the post-mortem examination gives. The paper highlights that while discrepancies between clinical and pathological diagnoses have significantly reduced in the last 30 years, they have not disappeared, and thus the post-mortem examination remains a vital audit of veterinary clinical practice and education. Also, while the authors indicate that much of this improvement may relate to advances in ante-mortem tests/procedures, they also note that alterations in personnel and the training of personnel in both clinical medicine and pathology can be a contributing factor. This further highlights the value of the post-mortem examination as a form of “quality control” on the knowledge accrued by the veterinarian and provides a vital role in training across all disciplines. The post-mortem examination should not be considered as an opportunity for the pathologists to gain the “upper hand” on a clinician, rather it should continue to be a valuable and respected learning process for both pathologists and clinicians. Of course while this is the mature and “politically correct” answer, what pathologist will not admit to having some degree of satisfaction in bruising the ego of a budding ego-maniac clinician. However, there is always reciprocation when the egotistic pathologist (yes there are some!) fails to find relevant lesions in a well worked-up clinical case.

Knowing the continued value of the post-mortem examination, it is of course a matter of concern that Dank and others (2012) have also highlighted the emergent universal problem that post-mortem examinations are now considered less attractive to clients and, in some cases, appear not to be encouraged by clinicians who feel the ante-mortem clinical diagnosis is sufficient. This clearly seems to be a greater problem in human medicine. Perhaps the authors are giving us a “wake-up call” by highlighting the fact that in veterinary medicine we could be trending in this direction. It is therefore imperative we preserve and nurture the post-mortem examination as it is one of the cornerstones of maintaining dialogue between clinicians and pathologists. There are tremendous opportunities for both parties to glean greater knowledge on disease mechanisms and evolving disease patterns from this relationship.

The importance of the post-mortem examination and pathology per se is not just unique to clinical medicine but is also of significant concern in the context of biomedical research. Research grants continue to be fuelled by the need to apply “sexy” technologies (genomics, deep gene sequencing, genome-wide association studies, gene knockout studies, proteomic profiling, metabolomics etc.) and it often appears to be difficult to excite reviewers with a statement such as “histopathological assessments will be undertaken”. Thus pathology can often be in the background of much high-profiled research. However time and time again the applications of these technologies, which, more often than not, use structureless tissue homogenates, generate mountains of data that require extensive analysis by informatical procedures. While this then culminates in a more refined data output, there continues to be a need to make it relevant to the disease process and/or to provide an accurate phenotype of the disease. Histopathological assessment remains one of the major methods of making this translation between the novel technologies and the actual disease process affecting the animal and also provides insights as to how disease processes in one organ can influence additional processes in that organ or in other body organs. With pathology remaining as a background to many high profile research programmes some disturbing problems come to light. Firstly there are projects in which “DIY” pathology (pathology practised by untrained pathologists) is practiced and published, often reducing what can be quite a sophisticated descriptive discipline to numerics illustrated in graphs. It is sad that in some instances the qualitative descriptive element can be overlooked in our modern obsession with often one-dimensional metrics. Secondly, one is constantly struck by the number of high-impact journals which produce histopathology images in the form of “thumb-nail” montages which cannot be enlarged to improve resolution. If the object of publishing is to allow the critical evaluation of the data, the least the pathologist should be able to see are reasonable images of lesions.

While pathology may be a path well worn it has advanced in tandem with advances in clinical medicine and biomedical research. Furthermore there is nothing on the horizon that is going to replace it. All disciplines flourish when there is a mutual respect for one another and with an understanding of the values that each discipline can bring in advancing our understanding of disease. Well done to Dank and others (2012) for highlighting this.


Professor Sean Callanan is a diagnostic and research pathologist at the School of Veterinary Medicine, University College Dublin. He is a member of the Royal College of Pathologists Specialist Advisory Committee on Veterinary Pathology and is current Vice-President of the European College of Veterinary Pathology.