Histology Techniques and Equipment

How is Tissue Prepared for Microscopic Examination?

Introduction to Tissue Processing

• The process of preparing tissue samples for microscopic examination involves several techniques and equipment used in pathology laboratories.

• Tissues, such as those from suspicious moles or cancerous organs, must be processed into thin slices comparable to paper for visibility under a light microscope.

Specimen Accessioning

• Upon arrival at the diagnostic pathology laboratory, tissue specimens come with a request form detailing patient information and tissue description.

• Each specimen is assigned a unique lab number that identifies it within the histology lab, ensuring accurate tracking and analysis.

Gross Examination and Fixation

• A pathologist or scientist conducts a gross examination to describe and measure the tissue before processing begins.

• Fixation is crucial for preserving tissues in a lifelike state; it should occur immediately after removal from the body to prevent degradation.

• Formalin (formaldehyde) is commonly used as a fixative depending on the type of tissue being processed.

Tissue Processing Steps

• After fixation, samples are placed into an automated tissue processor that removes water from the tissues and replaces it with molten paraffin wax.

• The embedding center maintains high temperatures to keep paraffin wax liquid while transferring tissue samples into molds.

Sectioning and Staining

• The microtome cuts very thin sections of the embedded tissue sample, akin to using a deli slicer; safety guidelines must be followed during this process.

• Thin sections are floated onto a warm water bath to smooth out any wrinkles before being transferred onto glass slides for further processing.