12th week

Ever since i got back from cytology, i have been at the shaving station in histo. Shaving is the process of removing excess wax and exposing the tissues in the embedded blocks. This will provide a smooth-sailing sectioning of the tissues. Shaving is done using the microtome machine. The difference between sectioning and shaving is, sectioning is done at 4-5 microns while shaving is done at 20 microns.

In addition, the person at the shaving station will be responsible for placing the tissue blocks which require decalcification into RDO. RDO is actually an acid which will decalcify the tissues. I have actually come across tissues which i cannot shave at all because it is too hard. For tissues of that nature, it will have to be placed in RDO even before it is shaved. For other tissues which do not require decalcification, they are placed in a detergent after shaving. This detergent will soften the tissue surface to the perfect level to which that it will be easier to section it. These blocks are placed in the detergent for five minutes and then washed under running water. If the blocks are placed in the detergent longer than five minutes, the staining of the sections on the slides will be compromised. Once, it was left in there for more than 5 minutes, blobs of stains were seen on the slides. This is perhaps due to chemical interactions. The detergent which has penetrated into the tissues will interact with the chemicals from the H&E stains.

There are many things to look out for during shaving. Firstly, score lines. Score lines are lines that appear on the surface of the tissue blocks. These lines are caused by the blunt blades. When score lines are observed, the blades must be removed immediately. Then, the blocks will be shaved again until the lines have disappeared. It is very important to ensure that after shaving a block which requires decalcification, the blade is changed to shave the next block. This is because, obviously, the blade will be blunt after shaving the hard tissue from the block which requires decalcification. If the blunt blade is used to shave a tissue block containing small tissues, it is hard to remove the score lines without taking the risk of losing the tissue after continuous shaving. Thirdly, removal of sutures and staples. Sutures are what seemed to be black threads used during an operation. Amazingly, sutures and staples are used by the surgeons during the operation for the orientation of the organs. Orientation of the organs aid in the trimming of the organs by the pathologists. Sometimes, i believe, unknowingly, when the pathologists trim the tissues into the cassettes, sutures or staples are hidden in tissues. The presence of the sutures and staples will apparently remain unknown throughout tissue processing as it does not distrupt the processing. It will usually be found during embedding and most of the time, during shaving. Which is pretty unpleasant. Not only will the staple or sutures cause the blade on the microtome to be instantly blunt, it will also require much digging and pulling out the staples and sutures from the hardened wax block. Fourthly, tissue blocks containing certain breast tissues are not required to be shaved. This is because they are exceptionally thin. Finally, i have to ensure that the wax in the tissue blocks are completely hardened before it can be shaved. This is to prevent the risk of the tissues dropping off from the block. When that happens, the tissue will have to be sent for re-blocking.

I realize that embedding affects shaving a lot. This is because, at times, the tissues are not on the same level in the wax. This is probably due to the tissues not being pressed down towards the mould during embedding. When the tissues are not on the same level, much shaving needs to be done to expose every part of the tissue. When this happens, the risk of losing parts of the tissues increases.


Nurathirah
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