What is karyotyping (classical/conventional/metaphase cytogenetics)?

Laboratory tests help classify multiple myeloma based on its genetic features.

In this video, we'll take a closer look at karyotyping. Also called classical cytogenetics, routine cytogenetics or metaphase cytogenetics.

Karyotype is a genetic test that analyzes the size, shape, and number of chromosomes in a sample of cells. In this lesson, you'll learn how this test is performed and what valuable insights it provides about the disease.

What is karyotyping?

In cytogenetics, karyotype is your essentially your DNA. It looks at when you have a bone marrow biopsy. They look at dividing cells and they look to see if there's any cytogenetic abnormalities.

We all have 46 two sets of 23 chromosomes, one from mom and one from dad. And that's your karyotype.

There are certain mutations that we pick up based on this karyotype and mutations that then have implications as far as their disease process.

Is karyotyping also called routine cytogenetics done on the blood or a bone marrow sample?

So routine cytogenetics as of now or karyotype is based on a bone marrow aspiration. Although there's looks at trying to do that without going through a bone marrow aspiration. It requires a bone marrow biopsy.

And then it's sent to specialty pathology labs that perform cytogenetics and or karyotype assessment.

There's different names for karyotyping one is classical cytogenetics. The other one is metaphase karyotype.

And what that test is, is we take the myeloma cells in a dish and we stimulate them to divide. And when they divide, we're able to capture them and we can see the, under the microscope, even the individual chromosomes, and we can count them and we can look to see if they are abnormal with the broken or, rearranged in some abnormal way.

And so that was the very first test that was used to look at genetics in cancer, and in multiple myeloma.

One of the most famous ones in cancer was what was called the Philadelphia chromosome because it was discovered in Philadelphia and it was in patients with chronic myelogenous leukemia.

And it was subsequently turned out that this chromosome represented a translocation or joining between chromosome nine and *22.

In multiple myeloma, we have similar events, and they form the basis for classification of multiple myeloma.

But curiously, those translocations in multiple myeloma are very cryptic, and they're hard to see in the conventional, cytogenetics or metaphase karyotypes. And for those we need we need to use other tests.

How many cells does karyotyping look at?

So it's very interesting when you stimulate the myeloma cells to divide in the dish. There's other cells that are besides myeloma cells that are in the bone marrow. And they often they don’t often divide much more readily than the myeloma cells do.

And so as you're looking through all these chromosomes that come from individual cells, usually what you're seeing is normal cells. And so you really have to hunt through the slide to identify ones which looks like they might be coming from the myeloma.

And to do that we looked through generally 20. We're trying to find 20 myeloma cells on the slide. And we're trying to look to see how many abnormalities they have.

But it is honestly it's quite laborious. And time it would be hard to do much more than 20 of those cells.

Who does the karyotyping or routine cytogenetics?

It’s done by researcher or ihematopathologist cytogeneticist in the laboratory and often what happens is it's very hard to get the myeloma cell to actually divide in the dish. to get the myeloma cell to actually divide in the dish.

And so it looks like the conventional cytogenetics is normal. And really that just means that we couldn't get the myeloma cell to divide and we couldn't analyze it properly.

So most of the time when we do this test in myeloma patients, it's normal. But that doesn't mean the myeloma cell looks normal. It just means the test failed.

Within multiple myeloma. Oftentimes, routines of genetics or classical cytogenetics are often normal. And that's because the plasma cells don't replicate as fast.

Whereas for instance, more aggressive diseases like acute leukemia oftentimes routine cytogenetics or classic cytogenetics will pick up mutations.

For myeloma, and sort of a deeper dive is the FISH analysis. So myeloma FISH panel will does not require cells to be replicating. And so it's much more sensitive to pick up mutations that would be missed otherwise.

And again that would be very helpful. You know prognostically. And also now therapeutically used to choice of regimens.

Why do the cells need to divide.

The cells need to divide it. Because when they divide they condense their chromatin and they condense their chromosomes. Small enough that they become visible.

And we can we can actually recognize each chromosome based on how big it is and what it looks like in a cell, which is not providing the, it's it's not possible to do that.

To better understand the laboratory technologies used to analyze genetic abnormalities in myeloma and assess your risk status, watch the other lessons in HealthTree University cytogenetic testing in myeloma course.