Histopathology (Processing)

Hi! This will be my second last post =D. I have been posted back to Histopathology lab since the last six weeks. For the four weeks, i went to processing and then went to main lab to do embedding for the next two weeks. As Zi Shuang have posted on embedding, I will talk about processing for this post. For processing, we used two types of tissue processor machine which are Leica and Peloris. For the morning batch of the trimmed tissues, they will be put into the Leica tissue processor. The program used will be extended 16 hours tissue processing whereby it is extended to 7.30am the following morning. For the afternoon batch, tissue sections will be put in the Peloris tissue processor. The program used will be the extended 9.5 hours Xylene free tissue processing whereby it is extended to 8.30am the following day. Thus, for this post I will be emphasizing on the Leica tissue processor.

Subject Title: Lab Technique

Topic: Tissue Processing

Below is a picture of the Leica tissue processor:


The cassettes rack used for this rack is shown below:



Principle: The principle of tissue processing is to remove the extractable water from tissue specimens and replace it with a medium that solidifies to allow sectioning. It consists of 3 stages which are dehydration, clearingand infiltrating. The purpose of dehydrating is to remove water from the tissue using graded alcohols from a lower to a higher concentration. Clearing is to remove alcohol from the tissue with a solvent that is miscible with paraffin wax such as xylene. Infiltrating is to infiltrate the tissue with paraffin wax to allow sectioning of tissues.

Steps involved:



I have observed that sometimes the tissue sections tend to sunk down or bulge up after they are processed and embedded. If the tissue sections are sunk down, it is normally due to the lack of infiltration. However, if the tissue sections are bulged up, it is normally due to the lack of dehydration.

I also observed that the cassette racks and the machine must undergo quick clean to wash off the reagents used for tissue processing. This quick clean process will take about 30 minutes. After this cleaning session, new cassette racks can then be loaded.

Some precautions to take note is that gloves should be wore at all times when you are at the trimming room. This is because you will be dealing with formalin when you are placing the tissue cassette in the formalin container for fixation before they are being processed. As formalin is carcinogenic, gloves can protect your hands from having contact with the formalin. Rinse with water immediately after you had accidentally splashed with formalin. Try to wear mask with shield to protect your eyes as formalin will cause eye irritation which will make you tear.

I will post until here for now =). If you have any questions, feel free to ask me =D.

References:

Picture of Tissue processor
www.dotmed.com/images/listingpics/370518.jpg

Lok Pui
0704138G