Section 2 -

Surgical Pathology Patrick Adegboyega and Martin Hale

The practice of histopathology is largely unchanged since the time of Virchow when he established it the 1850's. Although the principles of the technology are old, there are a number of advantages to this. Firstly, the equipment required is minimal and is relatively cheap to purchase at entry level, comprising, rotary processors and microtomes. In addition, the equipment can be expected to have a long service life if properly serviced and maintained. Tissue blocks embedded in wax are easy to prepare and store indefinitely and there are no specific environmental requirements other than good light to cut the H&E sections. Processing reagents are generally easily and readily available and there are no strict storage or transport requirements other than protection from fire. These advantages need to be compared with the requirements for the practice of Clinical Pathology. The analysers used in Clinical Pathology are complex instruments and have a high level of technology including the use of sophisticated computer interfaces. The equipment also has high maintenance requirements sourced from within the laboratory and from equipment suppliers. The reagents that are utilized are usually in the form of kits and have demanding storage requirements, often including the integrity of cold chains. Returning to histology, the processing of tissue is relatively straightforward provided that recognised standards and protocols are adhered to, such as, the number of baths, the frequency of solution changes and temperature ranges. It is important that histology laboratories do not look to achieve false economies or short cuts in any of these activities. Histopathology practice is founded on adequate tissue fixation and processing and any defects in fixation, dehydration, clearing and waxing impregnation may cause irretrievable loss, leading to sub-optimal diagnosis. In addition to the H&E stain there are a number of straightforward special stains that may be employed in the diagnosis of specific entities and infections, without resorting to complex immunohistochemistry and molecular techniques. The ever-increasing global onslaught of HIV infection and associated immunosuppression in affected patients highlights the need for timely diagnosis and optimal treatment as a basis for good disease surveillance and interventional strategies. Unfortunately, many of the regions most affected by this burden are in underdeveloped countries and so often lack the resources for the timely diagnosis and management of these disease conditions. Using an illustrative case presentation approach, the use of basic, reliable, readily available and cost-effective histochemical stains and techniques for the tissue diagnosis of infectious diseases in resources-limited settings will be discussed. This will include ways in which the histopathologist can be actively involved in the diagnosis and surveillance of emerging/re-emerging infectious diseases.