CELLULAR SCIENCES
examples include bone drills, bone forceps, male catheters, vaginal specula, spatulas and the surgical saw.
Advances in cellular pathology Modern-day dissection, which continues to rely heavily on the traditional tools discussed above, surprisingly has not progressed significantly over time. Our understanding of anatomy and physiology has progressed but our methods of assessing or evaluating macroscopic dissection procedures has relied mainly on surgical instruments used in the operating theatre, rather than improving on dissection instrumentation at the cut-up bench. The discipline of cellular pathology has
advanced tremendously and we have seen some very impressive improvements in the developing technologies. Some examples include the introduction of enclosed tissue processing machines, sophisticated paraffin embedding equipment, and improved microtomes for precision in section cutting. Most significantly, we have seen the rise of automation with the introduction of a plethora of variations on staining machines for routine haematoxylin and eosin (H&E) staining, special staining and immunocytochemical (ICC) staining procedures, and also have automated coverslipping machines. The growing developments in molecular technology and equipment also looks set to be an area of great expansion in the future. We have, perhaps, spent a great deal of
time perfecting and improving on new technologies without necessarily working out the parameters that ensure that the tissue we assess is optimal for the procedures we need to investigate. A classic case in point is the massive explosion of publications on the use of ICC in cellular pathology during the 1980s and 90s. There was great interest in developing automated platforms and also improving sensitivity for the detection of ever- smaller antigenic epitopes. However, as we attempted to identify an ever-increasing panel of antibodies to work on paraffin sections, recognition dawned that optimising tissue fixation and processing was more important to the final results than was originally believed. At this point we took tissue fixation and processing more seriously and also introduced the antigen retrieval procedures with which we are familiar today. But the first procedure undertaken on tissue in the cellular pathology laboratory is dissection.
Initial tissue dissection Information in the scientific literature on the importance of initial dissection and how accuracy and precision are achieved is hardly discussed. To an enthusiastic observer it appears a gaping omission! We have traditionally viewed histological dissection as quite a labour-intensive, fundamentally basic, yet highly skilled (in terms of those who perform it) practice. Yet we have not studied the variables of practice that
426 The next day I started drawing some
constructions and pondered on how something that was not dissimilar to a guillotine or bacon slicer could be used for histological dissection, the biggest issue being how to ensure precision and accuracy. The best option appeared to be adapting the devices on which we already rely (ie the microtome and micrometer) and modifying them for this purpose. With this in mind I approached a
Fig 2. Uneven and irregular tissue slice thickness from manual procedures.
contribute to inaccuracy and lack of precision. The devices used traditionally to measure
tissue at the cut-up bench have included the weighing scales and the metric ruler. There is very little consideration given to the need to ensure perpendicular sectioning of tissue and to ensure optimal tissue thickness (Fig 2). Thus, the appearance of tissue slices that have been measured by eye and by the metric rule can quite often be inaccurate and not perpendicular to the cutting face. This affects processing and embedding procedures, impacts on microtomy procedures, and also can affect ICC procedures and molecular investigations.
True cutting While standing at the delicatessen of my local supermarket, I watched a customer being served by the assistant; he lifted a large ham from the display counter, placed it on a bacon slicer, and cut several slices from the joint. He was unsure about how thin he could cut slices, but a glance at the Parma ham slices in the display in front of me told me what I needed to know. Later I read about the bacon slicer and
also about the guillotine, used popularly during the French Revolution for beheading and as the instrument of the death penalty prior to abolition of capital punishment in France. What was evident was how successful these devices had been, the reason being that they were perfectly constructed for the purpose.
commercial company (CellPath) and we discussed designs and formats. The literature in this area is not extensive and covers a wide spectrum of different approaches to tackling the needs of histological investigation. Some of the key factors that can affect accuracy and precision for histological dissection need to be appreciated, and include: • flat uniformity perpendicular to the specimen cutting face
• appropriate immobilisation of the tissue specimen during grossing
• good visualisation of the cutting tissue face • sharp knives with associated grossing equipment fit for purpose • grossing knife action.
Designs were constructed that attempted to take into account these factors. What ensued were considerations of not just final designs but also the materials to be used in construction of these devices. Trials of two devices were performed by staff at Viapath’s St John’s Histopathology Department (Fig 3) and in histopathology departments located at Guy’s and St Thomas’ NHS Trust. These two devices were named TruSlice
and TruSlice Digital (Figs 4a and 4b). TruSlice relies on the insertion of reinforced plastic inserts with defined recessed depths of 2, 3, 4 and 6 mm. The TruSlice Digital relies on the use of an attached micrometer. Both used a guillotine-like construction with a knife plate configuration that ensured perpendicular action of the blade. Preliminary trials were extremely positive
with good recordings of accuracy and precision. The findings were presented at last year’s IBMS Biomedical Science Congress as a short paper and also were published in the British Journal of Biomedical Science.1
St John’s Histopathology staff members. AUGUST 2016 THE BIOMEDICAL SCIENTIST
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