It occurs to me I haven’t described what happens to biopsies and surgical specimens that are sent to the lab. I have written about their loss, their mishandling, and even described a few odd foreign bodies. It’s time to remedy that oversight.
The biopsy in question will be a common one from the gut taken during a colonoscopy. If you have had this procedure all you probably know is you went into a surgical suite, were sedated, woke up in a recovery room, and then you were probably told the size of the biopsy taken, if any, and how many.
Let’s assume the biopsy in question for this post is one small piece about the size of a sesame seed.
The doctor who did your procedure is the ‘clinician’. He or she is the doctor working in the clinic. Eventually, they will be the person who receives the pathology report.
The doctor who will write that report is the pathologist. For the biopsy to go from the clinician to the pathologist requires many people and procedures.
First the biopsy must be put in a specimen jar with your proper name, medical number, and a description of what the specimen is.
Formalin is put on the specimen for our lab. The biopsy will sit in that for an hour up to half the day. How long depends upon the size of the biopsy. A tiny piece like the bowel biopsy I described will only have to stay in the formalin for an hour.
While the biopsy floats around in the formalin being fixed for the first stage of ‘processing’ in the lab, it is transported. Someone will carry it from the clinic or surgical suite to the ‘accessioning room’ in the lab.
Lab assistants work in the accessioning room. They collect he specimens as they are delivered and put relevant data in the lab computer system and assign the specimen a ‘surgical number’. They then put it in line to be ‘grossed‘.
Grossing is done by histotechs, pathology assistants, pathology residents, or pathologists. The photo above shows a small specimen being grossed. The ‘grosser’ will describe the biopsy, talking into a device that records their description while they work. Once the specimen is described and but up as much as necessary to process, it is put into cassettes.
The cassettes have the surgical number on them and the biopsy will stay with that cassette from that point forward.
The cassettes come in various colors as you can see by the photo. We use the colors to distinguish between types of biopsies. Some types are cut ASAP.
The cassettes are put in a basket and the basket is put on a processor. The process used to take the fresh biopsy removed the patient and eventually embed it in wax is slightly involved but is accomplished by transferring the biopsy from one solution to the next, letting it sit in each for a while. At the end of the process the biopsy needs to be ‘embedded‘. This is the point at which a histotech is necessary. Until this time, a lab assistant or pathology assistant took care of the specimen.
Embedding the biopsy requires the histotech recognize the types of tissue they are handling so they can orient it correctly. The tissue is placed in a metal mold and the mold is filled with paraffin. When the wax hardens, the tissue is suspended and we can cut it.
Cutting is done at a microtome.
A thin ‘ribbon‘ of paraffin with tissue is sliced from the face of the block. Again, this is done by histotechs. While is isn’t a difficult thing to do most of the time, it does take a lot of training. The histotech must recognize how deep to cut into the specimen and must be able to produce a flat and even section.
The first part of that process is called ‘facing the block‘. When doing that, the histotech watches to not only show all of the biopsy but also to make sure they don’t cut any more of the biopsy away than necessary.
Once the block is cut to the correct depth, a ribbon is taken. It is placed on warm water, floated on top so the heat can flatten it.
A glass slide is used to pick up the ribbon up off of the water.
Look closely at the photo and you can see the wax is being lifted off the water with a piece of glass.
The slide is then heated to remove the water and melt the paraffin. That adheres the biopsy to the slide permanently. At this point the slide can be saved but it can also be scratched and it has no color. Some will be saved but every case will also have another slide stained and protected with a thin piece of glass.
There is one stain that all biopsies and surgical specimens in our lab get, an H+E. The setup in the photo gives you an idea of the colors, orange and purple. On the biopsy, they look pink and blue. The slide in the above photo is the same tissue floating on the water. It was picked up with the glass slide, stained, and coverslipped with a thin piece of glass. The surgical number and other information is hidden by a white label.
The lab is now done. The slide is delivered to a resident or pathologist to ‘read’. Their training gives them the expertise to look at the microscopic details in the slide and know if it is normal or not. Under a microscope the above slide looks pink and blue. The nuclei of the cell is blue, which is DNA.
The rest of the cell is shades of pink. That is where all the proteins, fats ect. are stored in the body. It is also where the body manufactures the things it needs to live, heal, and reproduce.
The pathologist writes up the report. He or she will dictate what they see when they look at the slide, diagnose the disease, if there is one, and then a transcriptionist will listen to their dictation, enter it into a computer, and eventually that report will be sent to your doctor, the clinician.
So there it is, what happens to your biopsy in the lab. If you think about it, you might see all the ways things can go wrong but I would also like you to think about how much goes right. With this procedure, lives are saved every day.