You don’t have to be an oncologist to know that cancer is complicated.

There are stages, and measurements, and grades, and morphologies – it’s just a lot. But if you or a loved one are on the receiving end of a cancer diagnosis, making sense of the alphabet and number soup an oncologist gives your cancer is pretty vital.

Those numbers and letters are supposed to give everyone more information about your diagnosis, but if you don’t know what they mean, it can get confusing, fast. So in the hopes of giving you more context for when someone says “Stage 3” or “T1N0M0,” let’s go over the ABCs and 123s of a cancer diagnosis. [♪ INTRO] A cancer diagnosis is usually the result of a whole bunch of medical testing, from blood draws to X-rays or other imaging studies. But even when you’ve got that official cancer diagnosis, the next step isn’t necessarily treatment.

Because just knowing the cancer is there isn’t enough information. That would be like trying to prescribe an antibiotic for an infection without knowing what type of bacteria it was, or what antibiotics it was already resistant to. This is where staging comes in, and it’s an important step in figuring out where the cancer is, how big it is, and how to treat it.

And yes, it will involve more testing, like physical exams, X-rays, and biopsies. You’ve probably heard of some cancer stages, like you might know that stage 4 cancer sounds worse than stage 1. But there are lots of different systems and methods for staging cancer, and to figure out what stage you’re really at, your doc has to get a good look at the thing.

First, the doctors will review imaging results to visualize the cancer. CT scans, for example, will use something called contrast in order to differentiate cancerous cells from regular ones. And X-rays can also help identify growths because they show up as cloudy or white spots in darker tissue.

Based on the pictures, oncologists will stage the cancer using the numbering system that you may have heard of. But what you might not know is that cancer staging doesn’t start at 1, it starts at 0. And that 0 doesn’t mean there’s no cancer.

For instance, there’s a condition called ductal carcinoma in situ, or DCIS, that’s considered a stage 0 breast cancer. This is where funky cancerous cells were detected, but it’s limited to just the ducts within the breast, and hasn’t yet gotten into other tissues in the breast. Any diagnosis of in situ, which translates to original place, essentially means it hasn’t spread.

Which makes sense for a stage 0 cancer. After stage 0 comes the typical stages 1 to 4, which classify the cancer based on how it’s spreading. Stage 1 means that the cancer has spread to nearby cells, but it’s still tiny and located in the vicinity where it originated.

This is known as a localized cancer. Stage 2 indicates that the cancer has grown a bit, but still hasn’t spread beyond the original tissue. Stage 3 marks further growth of the tumor and its migration to other nearby tissues or lymph nodes.

The doctor might refer to this spread as “regional”, since it has moved around but stuck to the same neighborhood as where it originated. For example, if breast cancer spreads to the lymph node in your armpit, that would be considered regional spread. Stage 4 is the last stage of most cancers, and is when the cancer has spread to at least one other organ in the body, which doctors call “metastasis”, or sometimes “distant” spread.

But there’s one cancer that has a stage 5. It’s called Wilms tumor, and it’s the most common type of kidney cancer in children. When staging Wilms tumor, each kidney gets its own cancer stage, since most people have two of them.

And about 5% of the time, both kidneys have cancer cells. That’s stage 5. Within each of those stages, there can be letters added for more detail, such as how many sides of the organ have cancer, how large the tumor is, or how many lymph nodes it’s spread to.

For instance, with stage 2 prostate cancer, you’ll have stage 2A, which means the cancer is only on one side of the prostate, or stage 2B, where the cancer has reached both sides. But remember, this staging is just about spread, and it doesn’t necessarily correlate to the severity of the disease. Not all stage 4s are created equal!

Like, stage 4 Hodgkin's Lymphoma is still very treatable, and has between a 70-83% 5-year survival rate. On the other hand, stage 2 pancreatic cancer has a survival rate of just 44% after only 3 years. But what you may not know is that this system isn’t the only way to stage cancer.

There’s another scale called the TNM system that gets even more specific about the size and spread of the cancer. T describes the original, primary tumor’s size and invasiveness. N describes the nearby lymph nodes that the cancer has spread to.

And M describes the metastasis to other parts of the body. Each of these letters essentially gives its own bodily progress report from its respective location: the original tumor, lymph nodes, and other tissues. But it’s not just a letter.

Just like the number system, there’s more added to provide even more information. The TNM system uses the letter “X” when we can’t assess the cancer at that location. For example, TX or NX.

And sometimes you’ll even see “Tis”, to indicate the cancer is in situ, like some stage 0 cancers. But aside from those, the TNM system mostly uses numbers to quantify the spread at each of those locations. T can have a score of 0 to 4, with a bigger number meaning a bigger and more invasive primary tumor.

But the options for N only go up to three, with higher numbers meaning the cancer has spread to lymph nodes farther away from the original tumor. M is more of an on or off thing, with the 0 meaning there was no evidence of metastasis and a 1 indicating that the cancer has metastasized. And if you were itching for any more detail, they will sometimes add lowercase letters after these numbers to clarify things like how many places the cancer has metastasized to, like using M1b to indicate the cancer has spread to two or more areas.

So you might end up with a diagnosis of T3N1M0, meaning that your original tumor is getting big and has reached at least one lymph node near it, but your doctors have not found it anywhere else in your body. Okay, we’ve covered tumor size and spread. But if you’re squaring up with a cancer diagnosis, the real question you want to answer is how aggressive the cancer is.

As in, how fast is this cancer going to grow? To answer that question, doctors will have to put aside the X-rays and CT-scans and instead grab an old biology class reliable: the microscope. Doctors can assess how speedy your cancer is by zooming in to look at the morphology of cancer cells and compare it to your normal, healthy cells.

Healthy cells are referred to as well differentiated: they’ve got a job, and they have specialized their looks and behaviors to achieve that job. But when cells become cancerous, they tend to sort of regress, and they lose all those features and behaviors that made them good at being, say, kidney or brain cells. They end up looking immature and underdeveloped – just like me in high school.

And the less the cancer cells look like normal cells, the more they misbehave, and the more likely they are to spread. The process of comparing a patient’s cancer cells to healthy cells is called cancer grading, and doctors will use numbers to characterize that, too. Grade 1 means the cancer cells still look a lot like the healthy cells.

They’re what a doctor would call well differentiated, which also means they aren’t growing very fast. Next are grade 2 cancer cells, which look visibly different from the healthy cells. They’re growing fast and looking weird, and a doctor might call them moderately differentiated.

And finally we’ve got grade 3 cells, which are straight up weird. They grow and spread really aggressively, and they’re poorly differentiated, if at all. Some cancers have their own specific grading systems, but they all follow the same principle of higher numbers mean wilder looking cells, which means faster spread.

Whether it’s suspecting a diagnosis with lab tests, staging with imaging, or grading with microscopy, all of those results can help tailor treatment to that specific cancer. These are all just the early steps that help oncologists determine the best course of treatment based on their patient’s specific situation. And your doctor should go over the staging in detail.

If you have been diagnosed with cancer and been given a long string of letters and numbers, they’ll be able to spell it out for you. But hopefully this video helps you feel more comfortable decoding that alphabet soup, or at least, helps you explain it to everyone else. Cancer is weird, and there’s still a lot we’re learning about cancer and cancer treatments.

Case in point, we just made a video about how chemo can make some people’s hair turn curly! If you wanna check it out, the link is down below. Thanks for watching! [♪ OUTRO]