How to get the most out of your pathology submission (part 2)
Aaaand we’re back with part 2 of making a good pathology specimen. Today: What makes a good biopsy specimen? There are surprise pictures in this one but you’ll have to keep reading to find out of what (nothing gory, promise)
1) Take a good sample:
1a) Sample new, fresh lesions, not really advanced ones, if possible. This applies to skin (take the edge of a lesion or one that’s been there a couple of days, not 3 weeks) and a lot of other organs (if the liver looks cirrhotic, sample the most normal looking bit not the really nodular, fibrotic part). This is because these are the most diagnostic sections - the centre of an old lesion is usually just haemorrhage, necrosis, and fibrosis, none of which are bringing you any close to a diagnosis.
1b) Make your sample a sensible size. Really big samples don’t fix well, so if you need to take something large (a whole spleen for example) consider sending it overnight, fresh, and CHILLED. Miniscule samples are hard to trim and less likely to have good diagnostic information in them, so if it doesn’t have to be an endoscopic punch biopsy, don’t make it that.
1c) Please don’t cut into a tumor just to take a look. If you cut part way into your mass so you can see what’s in the middle, it makes it a lot harder for us to read margins because of the way the ink runs. I understand the urge, and I fully understand that you might not want to submit if it turns out to be something like at abscess, but cutting into it will make it harder for us to read margins and that does take away from what you’re getting. Aspirating is fine, but please try to avoid making cuts!
2) Fix your sample well! A poorly fixed sample will not only be delayed at the lab while we wait for it to fix, it’s also not going to give results. Why is it delayed? Unfixed biopsies are hard to trim well. We have to cut anything you give us into thin slices to even start the process of making a slide, and if it’s not firmly fixed we can’t do that well. Why is it going to give bad results? The longer we have to wait for something to fix, the more the cells are going to autolyse (break down). There is far less information in autolysis than in a sample where the cells look exactly how they did when they were still attached to the animal.
How do you fix a sample well? You should have a formalin:tissue ratio of 10:1 (if using 10% buffered formalin). That means ten times as much formalin as tissue. It’s annoying, I know, but it’s worth it. Also, if the sample is really fatty, consider using more formalin. Fat will partially dissolve into the formalin and make it less effective. For samples that are really bloody (spleens!) try to minimise how much blood makes it into the jar, because this fills up the formalin and then the formalin is wasted fixing all those loose blood cells instead of the tissue you actually want us to look at.
3) Use a sensible container: A good container should be hard to break (for posting, plastic is usually better than glass) and water tight (screw on lids are best). Most importantly, it needs to have a wide opening! If you have to squish your sample through the top when it’s fresh, we are not going to be able to get it out fixed. Samples fix to be very firm, so it won’t squish any more, and they often fix in weird positions - so if it’s something long and thin, it might fit through fine when you can hold it out straight but it won’t when it’s fixed curled up in a ball. Ideally pick a container where the opening is the same diameter as the container. That way you know that if the container is the right size, so is the opening. Good containers look like this:
Bad containers look like this:
4) Make margins or areas you are concerned about clear: If you are particularly worried about one part of a sample, that needs to be easy for us to figure out, and it needs to take into account that things look different once they’re fixed. For example: if you are submitting a uterus you just took out, and you think one ovary looks a bit off but it’s not 4 times the size of the other, find a way to show on the sample which one you’re worried about. Telling us left or right isn’t helpful when it gets to us and isn’t in the animal any more. It’s safer to assume that we won’t know what’s what by the time it gets to us. So you should utilise things like sutures, ink, or separate jars (cut the funky ovary off and submit it in its own pottle!) to make it obvious. And write down what that means on your submission form!
4a) Using sutures well for identification: Write down the colour and look of the suture you’ve used (eg: blue, smooth nylon or purple woven). This is especially important if you’re trying to mark out several things. You can also use different lengths of ends (but make it obvious, cut them very short and very long). More knots is hard to interpret, but more pieces (if they’re nice and close together) can work. We can take the sutures out once we’ve got all the infomation we need so it’s a good way to tell us things without risking negatively affecting what information you’ll get back.
4b) Using ink for identification: Ink can be great if you know what you’re doing. We ink things all the time to identify margins, so you need to make sure that what you’re doing won’t impede how we can then interpret it. If you really want to use ink, I would suggest calling your diagnostic lab and asking for advice. One thing you can do is ink a non-critical surface. What does that mean? If you’re submitting a skin mass, put ink on the haired skin side only. We don’t need any diagnostic marking on that surface because the top side isn’t a surgical margin. So if you want to put some ink on the hairy side, showing us which margin is which, that’s fine! Avoid putting ink on any aspect of the sample you have cut through, because those are the ones where ink can give us serious diagnostic information, so if it’s not done right you are going to lose out. In general I would say that the best markers you can use are ones that we can take off. Ink is permanent so again, if you’re not sure, don’t do it.
I think that’s everything I wanted to cover today folks! For posts on necropsy, histology, and filling in a submission form, check out the “pathology saturdays” tag. And as always, feel free to send in any questions or suggestions for future topics you might have!
