What are histology stains?
Histology and histopathology of biopsy samples are important in the diagnosis of skin conditions. They are frequently used in the detection and diagnosis of skin cancer.
- Histology refers to the study of the individual parts and structures which make up a cell, and the relationship between structure and function.
- Histopathology refers to the study of tissues that are abnormal or diseased.
Histology stains are used to colour different structures within the cells.
Before staining a slide, the tissue has to be prepared and mounted onto a glass slide.
The paraffin technique is the most common way to prepare a histological slide, and follows the following steps:
- Tissue sample is re-sectioned and fixed upon a slide
- Sample is dehydrated, then embedded in wax (paraffin)
- Tissue is sectioned and mounted
- Tissue sample is cleared then stained
- Tissue is then mounted on a permanent slide
Other common histological techniques include
- Frozen sections—tissue samples are frozen, sliced and sectioned with a cold blade, and then stained and observed
- The semithin technique—tissues are embedded in a medium like epoxy, which allows the sample to be sliced more thinly.
What are some types of histological stains?
Some of the most common types of stains include:
This is the most frequently used combination for general staining of skin samples, and is especially useful in the diagnosis and classification of cancer
- Haemotoxyln stains certain parts of the cell – like the nucleus – blue
- Eosin stains other parts of the cell – such as the cytoplasm – red or pink.
Mucin stains are best for the detection and dyeing of mucopolysaccharides. Examples of mucin stains include:
- Alcian blue
- Period acid-schiff (PAS).
Melanin stains, as the name implies, are used for dyeing melanin and are commonly used in the diagnosis of melanoma. One common example of a melanin stain is the Fontana-Masson.
Trichrome stains use a combination of three different dyes to achieve their effect. These are specifically used to dye lipids. Common trichrome stains include
- Gomori trichrome
- Mallory trichrome,
- Sudan stains. One particular Sudan stain, known as Red Oil O, is frequently used in the diagnosis of fat emboli in the lungs.
What are some common histological stains?
The table below gives examples of different histological stains.
What are the advantages and disadvantages of conventional histology?
The advantages of histology and histological staining are:
- It is one of the least expensive morphological methods
- Allows for the study of large sections of the tissue sample
- Can be collected fairly quickly and with little or no risk to the patient
- Gives clinicians an important diagnostic tool and allows them the ability to examine the internal architecture of various cells and tissues
The disadvantages of histology and histological staining include:
- Preparation of the slides using the paraffin technique can be time-consuming; frozen slides are faster to prepare but this can affect the resolution, especially when using light microscopy
- Technique is subject to human error during the preparation and analysis of slides
- This type of staining can be less specific than specialty staining techniques like immunohistochemical (IHC) staining.
- It can sometimes be difficult to identify certain types of cells with this technique, which can affect its value as a diagnostic tool