Van mikroskoop tot molekuul - nuwe uitdagings vir anatomiese patologie

Abstract

The discipline of Anatomical Pathology has an interesting history. Surgical pathology has come a long way since Antoni van Leewenhoek of Delft invented the microscope in the early 17 th century. This was followed by Malpighi who contributed not only to the postmortem skills of those days but also to the development of the discipline of histology. The greatest figure and a great teacher of Anatomical Pathology was Rudolf Virchow in the late 19 th century. Anatomical Pahtology and particularly surgical pathology was not well accepted by clinicians. Valpeau who was a famous professor of clinical surgery at the Paris University, states in his work on diseases of the breast which was published in 1853 - and I quote: "The intervention of the microscope is not at all necessary to decide whether such and such a tumour which is being removed is or is not of cancerous nature" Despite his comments, the surgical biopsy was introduced as an essential diagnostic tool as the University of Berlin in the 1870s and Friedrich von Esmarch, Professor of surgery at the Kiel University, presented forceful arguments on the need to establish a microscopic diagnosis before performing mutilating surgical procedures for suspected malignancy. Shortly thereafter the freezing microtome was introduced and the frozen section procedure hastened the acceptance of the surgical pathologist as an indispensable member of the clinico-pathological surgical team. Other disciplines followed suit and soon they also accepted the anatomical pathologists' contributions to the patients' well-being. Lauren Ackerman, a well-known American surgical pathologist who is the author of a textbook on surgical pathology, masterfully describes the characteristics of the surgical pathologist as follows: "the modern surgical pathologist is closely affiliated with many branches of medicine" The microscope has changed over the years but it still remains the single most important instrument for the anatomical pathologist, much as the stethoscope is for a physician. The microscope has changed over the years but it still remains the single most important instrument for the anatomical pathologist, much as the stethoscope is for a physician. In the 1950s electron microscopy was developed and added to the diagnostic capability of pathologists, particularly in the field of renal pathology and tumour pathology. The most recent development in microscopy is the confocal laser microscope which is capable of giving a three-dimensional image of a thin microscopic section. Over the years many special techniques were developed. These include special stains for certain cells and cell products, enzyme histochemistry which is of particular use in the diagnosis of diseases of skeletal muscle, and electron microscopy in the development of diagnostic techniques for remal pathology and tumour pathology. This was followed by immunohistochemistry where immunological methods were used to identify certain cells, cell products or infectious agents. There is probably no other method that has revolutionized anatomical pathology to the same extent during the past 50 years. More recently, flow cytometry came into use which made it possible to determine the amount of DNA in tumour cells. The analysis of cell proliferation is also done by using immunohistochemical techniques. Modern molecular techniques, based on the polymerase chain reaction, caused another revolution. They allow for small fragments of DNA sequence to be amplified in order to form millions of copies of DNA sequence which can be analysed. A major advantage of this technique is that paraffin-embedded tissue can be used and one can also make use of thin micro-scopic sections of tissue. Another modern technique is in situ hybridisation which is a sensitive method for the detection of gene expression at cellular level. DNA or RNA probes are used to identify chromosomal abnormalities or viruses and other micro-organisms in tissues. This technique can also be used on thin sections and by combining it with immunocyctochmeical techniques, the results can be visualised.