Week 5: Histopathology Lab

Name: Nadiah Sukma
Admin number: 0705365E


hello people..

it is now my turn to share the experiences ive gained within this 5 week of very-tiring-yet-fun SIP... First, i have to explain the different parts of the working area. According to our schedule we'll be posted to 4 months of Histopathology lab and a month of Cytology.
In Histo lab, there are;

1. Outside area

• Reception/ Specimen sorting room
• Trimming room

2. Inside area- Main lab

• Embedding
• Microtomy
• Staining (H&E and Special Stains)
• Sorting slides + Verification of patient's form + Signed out to the respectives pathologists

For this month, im posted to the outside area (but most of the time im in the trimming room, assisting the pathologist).

All specimens that comes, will be received at the reception room, where the technologists have to first, verify the specimens against the checklist. If nature and the number of specimens (Specimens A, B anc C etc) correspond to the ones listed on the checklist, they are initialed, electronically dated and billed. Second, all the specimens are then given individual biopsy number (eg PB XXXXX) which will be its ID throughout the whole process.

The specimens will then be sorted out. The small and simple biopsies (eg; polyps, certain gallbladder and appendix) are given to technologists for them to pass (not necessarily trim, cos some are too small) and the large and complex specimens (eg; breast, liver, lung, kidney, nose, colon, ovarian cysts + fallopian tubes, enlarged gallbladder and prostate gland) are for pathologists to trim.

[[fyi: all specimens comes in a bag of formalin to be fixed. they have to be sufficiently fixed for atleast 6 hours before being trimmed]]

and..... all trimmings are done in the trimmning room... (haha!) thats where my main job is... which is to assist the pathologists. there are 3 stations in the room, so 3 pathologist are able to trim at a time. but sometimes more pathogists come in to do other stuff and thats just plain havoc for me...hehe

Before trimming, i have to prepare a set of cassettes (remember during HTech we use green colour cassette to embed?) for each specimens; labelling them with patient's ID, specimen ID and block ID. Then prepare the request/patient's form for pathologists. bla bla bla... n other necessary stuff.....that, in a way or another assist them in their trimming... hehehe

After trimming, the blocks are placed into an automated tissue processor. The process takes around 9.5 hours but is left over night (coz our lab, no night shift) and will be ready at the time that we set (eg; 7.30 am)

Principles of tissue processing:

3 stages of the tissue processing are designed to remove the extractable water from the tissue specimens and replace it with a medium that solidifies to allow sectioning. It must be firm enough to support the tissue and give it the rigidity and at the same time must be soft enough for the knife to cut through the tissue into thin sections with little or no damage.

1. Dehydration of tissue

Since the specimens are prior fixed in formalin, dehydration is to remove both water and the fixative (formalin) from the tissue using graded alcohol (dehydrating fluid). This step is essential because paraffin wax will not penetrate the tissue in presence of water and placing the specimens directly into 100% alcohol will distort the tissue.

2. Clearing the tissue

Since alcohol (dehydrating fluid) is completely not miscible with wax, it has to be removed from tissue and replacing it with fluid that is completely miscible with both dehydrating fluid and embedding medium (paraffin wax). common eg; xylene.

3. Infiltrating the tissue with paraffin wax.

Replacing the clearing agent with paraffin wax; infiltrating (impregnating) the tissue with embedding medium. Specimens are transfered from the clearing agent to molten wax at 60C and diffusion will occur. This step is different from the embedding step itself because at this stage the wax provides support internally and externally to the tissue.

Factors affecting tissue processing rate:

1. Agitation

Too slow => ineffective

Too vigorous => cause damage to soft and friable tissue.

2. Heat

Heat increases the rate of penetration.

3. Viscosity

Low viscosity => easier to diffuse into tissue

4. Vacuum

Removes air bubbles trapped within the tissue and able to bring the processing fluids into more intimate contact with parts of the tissue.

[i dont think stating the steps involved in the processing is appropriate, because there are many type of processing, each different in length time eg; 9.5 hr, 13 hr, 16 hr, and the steps involved are also different]

At the end of the processing, the blocks are ready to be embedded, sectioned and stained. (main lab)

and anw, unlike rachael, i didnt have the chance to witness a post-mortem.. =(

*First posted on THURSDAY 23 july, last editted on Monday.

=) =) =)