Pathology, histopathology or histology aims to study the manifestation of disease by microscopic examination of tissue morphology. In pathology, the sample to be examined under the microscope usually is the result of a surgery, biopsy or autopsy after fixation, clearing/embedding and sectioning of the tissue specimen. Alternatively, frozen section processing with a cryostat is done when rapid results are required (e.g. during surgery) or fixation would be detrimental to target structures such as lipids or certain antigens. The tissue sections after fixation and wax embedding are typically cut into two to five micron thin slices with a microtome before staining and transfer to a glass slide for examination with a light microscope. Typical specimens in pathology are colon, kidney, pancreas, cervix, lung, breast, prostate, or connective tissue.
While various staining procedures for human/animal and plant tissues have been developed as early as the 17th century it was the German physician Rudolf Virchow who is being considered the father of modern histopathology. Virchow realized the potential of the emerging new microscope techniques of the 19th century for his groundbreaking research, published a vast amount of scientific writing and created an impressive collection of thousands of histopathological sample slides, thus building the foundation of modern histology and cancer research.
Histology slide preparation begins with fixation of the tissue specimen. This is a crucial step in tissue preparation, and its purpose is to prevent tissue autolysis and putrefaction. For best results, the biological tissue samples should be transferred into fixative immediately after collection, usually in 10% neutral buffered formalin for 24 to 48 hours. After fixation, specimens are trimmed using a scalpel to enable them to fit into an appropriately labelled tissue cassette that is stored in formalin until processing begins.
The first step of processing is dehydration, which involves immersing your specimen in increasing concentrations of alcohol to remove the water and formalin from the tissue. Clearing is the next step, in which an organic solvent such as xylene is used to remove the alcohol and allow infiltration with paraffin wax. Embedding is the final step, where specimens are infiltrated with the embedding agent – usually paraffin wax which provides a support matrix that allows for very thin sectioning. A microtome is used to slice extremely thin tissue sections off the block in the form of a ribbon, following histochemical staining (typically haematoxylin and eosin - “HE stain”) to provide contrast to tissue sections, making tissue structures better visible and easier to evaluate. In certain cases immunohistochemical stainings (IHC), such as HER2 or Ki-67, are required for further analysis.
A very good differentiation of tissue structures and clearly visible cellular details are absolute prerequisites in pathology for carcinoma and tumor cell diagnosis. Histopathologists rely on crystal-clear images of their samples with the highest color fidelity in brightfield. Other contrasting techniques include polarization, CISH, fluorescence, immunofluorescence, or FISH microscopy. While histological and immunohistochemical stains result in a good transparency of the sample and specific staining of cellular features, it is the optical quality of the microscope, the fidelity of the attached camera for digital documentation, and the ergonomic design of the instrument that can make all the difference when screening patient samples. Automated digital slide scanning systems with class-leading optics assist with high-throughput screening and archiving.
ZEISS Axiolab 5
Axiolab 5 is made for the clinical routine work that goes on every day in your histopathology lab. The white LED illumination with very high color rendering index allows you to visualize your H&E and IHC stained histological samples in true color. The constant color temperature of the LED and the light manager facilitates system operation and digital documentation. Combine Axiolab 5 with the microscope camera Axiocam 208 color and take full advantage of the smart microscopy concept: you'll be experiencing a completely new form of digital documentation in your daily clinical routine. Just focus your sample and press a single button for crisp 4k images in true color. The digital image will look exactly like you see it through the eyepieces, with all the details and subtle color differences clearly visible. A scale bar in the image is automatically included. To store images with the respective patient ID Axiocam 208 color can readily be integrated with laboratory information systems that support Twain. For fluorescence, the powerful LEDs in various wavelengths are both energy efficient and easier to handle than conventional HBO illumination.
ZEISS Axioscope 5
Axioscope 5 with Axiocam 208 color makes examining and documenting your H&E and IHC stained slides very efficient. It offers an Ergo-stage, that allows to individually adapt and fix the stage handle in a comfortable position. The dual specimen holder means fewer slide changes – for example, when you're examining IHC slides. With the very high color rendering index LED you will clearly see the subtle differences in your stained samples in true color and experience all the advantages of LED illumination such as stable color temperature, low energy consumption and long lifetime. This robust and smart microscope makes automatic adjustments for brightness and white balance to keep digital documentation for your clinical routine tasks easy. All you have to do is focus on your sample, press the ergonomic Snap button on the microscope, and that's it. A scale bar in the image is automatically included. Due to the 4k image even challenging samples like Heliobacter pylori or Ziehl Neelsen stained mycobacteria can be clearly visualized. Additional measurement and counting tools, as well as image sharing possibilities are available with the easy to use software Labscope. The true color, high resolution (4k) live image, allows for discussions of critical cases with colleagues right on the monitor. Combine Axioscope 5 with the LED light source Colibri 3 and the sensitive, standalone microscope camera Axiocam 202 mono to have the perfect setup for easy multichannel fluorescence documentation - even without a PC.
ZEISS Axioscan 7
Digitize your specimens with Axioscan 7 – the reliable, reproducible way to create high-quality virtual microscope slides. Axioscan 7 combines qualities that you would not expect to get in a slide scanner: high speed digitization and outstanding image quality plus an unrivaled variety of imaging modes are all available in a fully automated and easy to operate system. Capture virtual slides quickly with high-speed scanning, while retaining consistently high quality, whether you want to capture brightfield, fluorescence or polarized light images.
Application Note: ZEISS Axio Scan.Z1
A Reference List for Automated Slide Scanning
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