Histology is the study of tissues, and one of the most critical aspects of this field is staining. Stains allow scientists, pathologists, and researchers to visualize tissue structures under the microscope, highlighting key components and making it easier to diagnose diseases or conduct research. However, not all stains are the same—there are several types, each suited to different purposes. In this article, we will explore the differences between histology stains and how they are used to analyze tissue samples.
What Are Histology Stains?
Histology stains are chemical dyes used to enhance the contrast of tissue samples viewed under a microscope. Since most biological tissues are transparent, staining is necessary to differentiate cellular structures, proteins, and other components. Different stains target specific tissue elements such as proteins, lipids, or nucleic acids, allowing for detailed visualization and interpretation.
The Most Common Types of Histology Stains
Several types of stains are widely used in histology, each with its own unique characteristics and applications. Below, we break down some of the most commonly used stains and their key differences.
1. Hematoxylin and Eosin (H&E) Stain
Hematoxylin and Eosin (H&E) is the most commonly used histological stain, especially in medical diagnosis. This stain offers a general overview of tissue structure, making it essential for examining the morphology of cells and tissues.
- Hematoxylin: Stains the cell nuclei blue or purple by binding to acidic components, such as DNA and RNA.
- Eosin: Stains the cytoplasm, connective tissue, and extracellular matrix in various shades of pink or red.
Application: H&E staining is typically used in routine pathology and histology for detecting tumors, inflammation, or abnormal cell morphology. It provides a clear contrast between the nucleus and cytoplasm, making it ideal for examining the general architecture of tissues.
2. Periodic Acid-Schiff (PAS) Stain
PAS stain is widely used to detect polysaccharides such as glycogen, as well as mucins and basement membranes. This stain is essential for identifying carbohydrate-rich molecules within tissue sections.
- Periodic Acid: Oxidizes carbohydrates in tissues, creating aldehyde groups.
- Schiff Reagent: Reacts with the aldehyde groups, producing a magenta or deep pink color.
Application: PAS staining is frequently used in liver biopsies to identify glycogen storage diseases, fungal infections, and certain types of cancer. It is also useful for identifying basement membrane damage in kidney tissue.
3. Masson’s Trichrome Stain
Masson’s Trichrome is a multi-component stain that differentiates among muscle, collagen, and fibrin in tissue sections. This stain is especially useful for identifying fibrotic changes in tissues.
- Three components: Masson’s Trichrome uses three different dyes—hematoxylin (staining nuclei), Biebrich scarlet-acid fuchsin (staining muscle and cytoplasm), and aniline blue (staining collagen).
Application: This stain is commonly used in cardiac, liver, and kidney biopsies to detect fibrosis, as well as in skin biopsies to assess connective tissue diseases. It is particularly helpful in distinguishing between collagen and muscle tissues.
4. Silver Stains
Silver stains are specialized stains that highlight specific tissue elements like nerve fibers, reticulin fibers, and certain microorganisms. These stains use silver salts to deposit metallic silver onto tissue sections.
- Silver staining process: Tissue elements such as reticular fibers or fungi reduce silver ions to metallic silver, which appears as black deposits.
Application: Silver stains are particularly useful in neurohistology for visualizing neuronal structures and reticular fibers. They are also essential in microbiology for identifying certain fungi, bacteria, and spirochetes.
5. Giemsa Stain
Giemsa stain is a differential stain that is primarily used in hematology to examine blood smears and bone marrow samples. It is part of the Romanowsky staining family.
- Staining properties: Giemsa stain binds to nucleic acids, with DNA staining dark blue to violet and cytoplasm staining lighter shades of pink or blue.
Application: Giemsa staining is critical for identifying blood parasites (like malaria), white blood cell disorders, and bone marrow abnormalities. It is also used to study chromosomal aberrations and detect Helicobacter pylori in stomach biopsies.
6. Congo Red Stain
Congo Red is a specialized stain used for the detection of amyloid deposits in tissues. Amyloid proteins are misfolded proteins that can accumulate in organs, leading to conditions like amyloidosis.
- Congo Red characteristics: Amyloid deposits stain red under light microscopy and exhibit a characteristic apple-green birefringence when viewed under polarized light.
Application: Congo Red staining is vital for diagnosing amyloidosis, a condition where amyloid proteins build up in tissues and organs. This stain is particularly useful for liver, kidney, and heart biopsies.
Comparing Histology Stains: Key Differences
While all histology stains are designed to highlight specific tissue structures, their chemical properties, target components, and applications vary. Below are some of the key differences between these stains:
- Specificity: Some stains like H&E provide a broad view of tissue structure, while others like PAS or Congo Red are highly specific, targeting particular tissue elements like carbohydrates or amyloid proteins.
- Complexity: Simple stains like H&E involve just two dyes, while stains like Masson’s Trichrome or Silver stains involve multiple components and complex processes.
- Diagnostic Value: While H&E staining is used in routine diagnoses, specialized stains like Giemsa or Congo Red are essential for diagnosing blood disorders or amyloidosis, respectively.
- Visualization Techniques: Some stains, like Congo Red, require specialized equipment such as polarized light microscopy to reveal their unique properties, while others like H&E and PAS can be viewed under standard light microscopy.
Choosing the Right Histology Stain for the Job
Choosing the correct histology stain depends on the specific research or diagnostic need. Pathologists often rely on H&E as a starting point for general tissue analysis, while specialized stains are used to investigate specific components like collagen, microorganisms, or amyloid proteins.
Contract Laboratory has helped many companies with their Histology projects. Below are some examples of Histology Test Requests:
- CAP or CLIA-certified histology laboratory is needed to process and analyze paraffin blocks of human skin samples that we would like to have cut for slides, and then subsequently analyzed for H&E and Gomori’s Trichrome.
- Europe University Researcher needs a histology laboratory for Immunohistochemistry for CD52 on a tissue slide (paraffin-embedded, formalin fixation.
- FDA GMP Medical Device Laboratory needed for biocompatibility testing of polypropylene mesh for medical use for a 510(k) application in accordance with the Blue Book Guidance G95-1, (Use of International Standard ISO-10993, Biological Evaluation of Medical Devices Part 1: Evaluation and Testing), acceptable test results should be supplied for the biological tests listed below. Standard protocols such as those identified by the USP or ASTM should be used in conducting the biocompatibility testing, if possible. Such tests should be performed on devices ready for surgical use (i.e., after manufacture, sterilization and packaging for commercial distribution). Cytotoxicity Sensitization Irritation or Intracutaneous reactivity Systemic toxicity (acute) Genotoxicity Implantation (with histology of the surrounding tissue) Hemolysis Pyrogenicity For products that remain in the body for greater than 30 days, the following additional tests are recommended: Subchronic toxicity Chronic toxicity Long term carcinogenicity studies should be performed with any device in which a positive genotoxicity test result was obtained.
- LONG-TERM: Preclinical CRO Immunology/Histology Laboratory needed for Non-GLP histological processing from buffered formalin-fixed tissues (human and animal, size 6 mm diameter, approx. 40 um thick) into H&E stained slides (at 3 different levels) and about 10 FFPE unstained slides for further subsequent immunohistochemistry,
- France University researcher needs a histology laboratory for Immunohistochemistry on 1 slide (TMA) for research antibodies (already purchased or not, example ALDH, SOX).
And many more. View other Histology Staining View Laboratory Test Requests for Histology Staining
If your pharmaceutical company, hospital, health clinic, or other healthcare facilities needs histology laboratories for histology staining, submit a Histology Laboratory Test Request.
