Yesterday I visited the Histology Laboratory at work. Now, before I started working here I had no idea what histology was. Probably a bit ridiculous but I’m a real believer in the fact you don’t know things when you’ve just never come across them before and clearly my path had never crossed anything relating to histology before! For those like me without a clue, histology is the study of looking at tissues in microscopic detail. It’s what happens when a biopsy is taken, for example, and is then studied in detail to determine what is going on.
It is important for me to understand these processes because often during a post mortem histological samples for testing will be requested by the pathologist. They will normally take pieces of organs and place them in pots with formalin (a solution of water and formaldehyde) or in what is known as a block and then into the solution and we will take these samples up to the lab. That is where my knowledge ended, but now I know what happens after and it’s really interesting so I thought I would share!
We take our boxes up to the lab and then leave them on a shelf. In the box are the samples and a form that we have filled out with all the details of the patient and the samples taken. Next, someone from the lab will check that the samples in the box match what is described on the form, any discrepancies and these are sent back to the department to be checked. The guy showing me around says this happens all the time but I’ve never seen any returned to us before- clearly the mortuary is better than other places!!
The samples then move onto another area where they are described in detail and measured, and then placed into blocks if not already. The block is like a small plastic case with a metal lid, and these have holes all over. The blocks are printed with a label saying what they are and an individual number given to each one to identify it. Next, a machine known as a processor is loaded with the blocks. This works to remove any water from the samples, then fill them with a chemical called xylene and then it finally removes the xylene and fills the block with molten wax at 60 degrees centigrade. The processor can work overnight on a 12/13 hour cycle or for shorter or longer if necessary. The blocks come out of this machine with the sample in a block of wax. The blocks can be stored up to 20 years at the hospital.
After this, someone scrapes the sides off of excess wax and the blocks are passed on to another group of people. These people place the wax blocks into another machine called a microtome. The microtome shaves off a slice off the block that is 3 thousandths of a millimetre thick. Teeny tiny. The blocks are held on ice before they go into the machine and then the handle is turned and tiny slices are taken off. A tiny slice is removed and then floated in a bath of water at 50 degrees centigrade which flattens it out and removes any crinkles. The fact it is just below the molten temperature is intentional. A glass slide is placed into the water bath and picks up the tiny slice, and that is what we know as slides! I noticed the microtome we were using had a sticker with Black Widow (member of Marvel’s Avengers) on it and I queried only to be told they have to name them all separately so they know which machine they are referring to!
One more stage is left with the machines and that is to dye the tissue in the slide. You may have seen pictures of cells where they are a real deep purple colour. That is from the dye, were the dye not applied you would really struggle to see anything under the microscope. Slides complete and dyed, they are matched back to the form from the start and then passed on to the consultant to examine and determine a diagnosis. Right before they are passed on a quality check is performed to ensure the slides show what they need to and are of a good quality. It’s a very intensive, thorough and effective process that happens in this lab! There are 21 people who work there and they process work for 12 consultants. The slides are kept for up to 15 years at the hospital for reference in case they need to be looked at again. 34,000 samples go through this lab each year and they are insanely busy from what I could see on my short visit.
I’m hoping to go back and see some more of what happens in the lab, but for now I really fee like the insight I gained was invaluable. You really don’t realise what happens behind the scenes and the work that goes in until you see it for yourself! I hope you found this an interesting as I did and have had a good start to your week!
Good report. Just a minor comment. Tissues are placed in a cassette After the tissue has been processed and embedded in wax, it then becomes known as a block.
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Thank Carol! I knew I’d have noted something down incorrectly as I scribbled things down!