Histopathological Techniques


Histopathological techniques are methods used to study the microscopic structure of tissues and cells, particularly for diagnostic purposes in medicine and research. These techniques involve preparing tissue samples, staining them to enhance specific features, and examining them under a microscope. 


Common Histopathological Techniques

01. Sample collection: sample collection is a crucial initial step in histopathological analysis, as it directly impacts the quality and reliability of subsequent analyses. The process involves obtaining tissue or cellular samples from patients or experimental subjects.

  • Biopsy: Biopsies involve the removal of a small piece of tissue from a specific site for examination. Depending on the location and nature of the tissue, different biopsy techniques may be used, such as needle biopsy, incisional biopsy, or excisional biopsy.


  • Surgical resection: In cases where larger tissue samples are needed or when a definitive diagnosis requires the removal of an entire organ or lesion, surgical resection is performed. This may involve procedures like tumor resection or organ removal.


  • Fine needle aspiration (FNA): FNA involves using a thin needle to extract cells or small tissue fragments from a lesion or mass. This technique is commonly used for sampling superficial or easily accessible tissues, such as the thyroid, breast, or lymph nodes.


  • Brush cytology: This technique involves using a specialized brush to collect cells from the surface of organs or lesions, such as the cervix or urinary tract. The collected cells are then transferred onto slides for cytological examination.


  • Endoscopic or laparoscopic biopsy: Endoscopic or laparoscopic procedures allow for the visualization and sampling of internal organs using minimally invasive techniques. Biopsy forceps or brushes are passed through an endoscope or laparoscope to obtain tissue samples.


  • Cytological smears: For certain tissues or lesions, cells can be collected by gently scraping or swabbing the surface and then transferring them onto slides for cytological examination. This is commonly done for samples like cervical smears for Pap testing.


02. Fixation: The tissue sample is preserved using a fixative solution (commonly formalin) to prevent decay and maintain its structure.


03. Processing: The fixed tissue is dehydrated using a series of alcohol solutions, cleared with a solvent such as xylene, and embedded in a solid medium (usually paraffin wax) to provide support for sectioning.


04. Sectioning: Thin slices (sections) of the embedded tissue are cut using a microtome. These sections are typically around 5-10 micrometers thick.


05. Staining: Stains are applied to the tissue sections to enhance the contrast and visibility of specific structures. Common stains include hematoxylin and eosin (H&E), which stains nuclei blue-purple and cytoplasm and extracellular matrix pink, and special stains for highlighting particular tissue components or pathogens.


06. Mounting: The stained sections are mounted onto glass slides and cover slipped for protection.


07. Microscopic examination: The prepared slides are examined under a light microscope by a pathologist or researcher. They observe the tissue architecture, cellular morphology, and any abnormalities present.


08. Image analysis: In some cases, digital image analysis techniques may be employed to quantify and analyze features of interest in the tissue samples.


These techniques are fundamental in diagnosing diseases, monitoring treatment responses, and advancing our understanding of various pathological processes. They are widely used in fields such as pathology, oncology, histology, and research laboratories.


References:

  • Labtron Vibrating Microtome LVMI-A10 | Image Science (no date) Available at: https://imagescience.hu/products/labtron-vibrating-microtome-lvmi-a10/ (Accessed: 28 March 2024).
  • Mohan, H. (2013) Pathology practical book. 3rd edn. New Delhi: Jaypee Brothers Medical Publishers.
  • TISSUE PROCESSING (no date). India: National Institute of Open Schooling.
  • Mohan, H. (2013) Pathology practical book. 3rd edn. New Delhi: Jaypee Brothers Medical Publishers.
  • Hematoxylin and Eosin Staining Kit | K1485 | BioVision, Inc. (no date) Available at: https://www.biovision.com/hematoxylin-and-eosin-staining-kit-26682.html (Accessed: 28 March 2024).Automated slide stainer MYREVA SS-30 (no date)  Available at: https://www.biotec-co.com/e/index.php?route=product/product&product_id=69 (Accessed: 28 March 2024).
  • TRANSPORT OF CLINICAL SAMPLES (n.d.). NHS: North Cumbria University Hospitals . 



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