I used to think of my tonsillectomy as a one-off procedure I’d had when I was in kindergarten, looking back fondly on the days recovering and sipping Slurpees. A decade later, I was taken by surprise when my doctor did the routine tongue-depressor look at my throat and remarked that my tonsils looked a bit inflamed.

It turns out, even after you’ve had your tonsils surgically removed, they can grow back. 

Your tonsils are spheres of lymphoid tissue that meet with the base of your tongue in the back of your throat. In toddlers, tonsils serve as a useful part of the immune system’s ability to fight infections by reacting to the germs little kids naturally take in. As you age, your tonsils play an insignificant role in your immune system, and in most adults they’ve shriveled up and disappeared. Your body can fight off pathogens by the time you reach adulthood, and more important parts of the immune system take over the heavy lifting from your tonsils.

There are two reasons why your tonsils might make a triumphant comeback. The first is that your surgeon accidentally left some of the tissue behind. The second is that your surgeon intentionally left some of the tissue behind.

If you’re getting a full tonsillectomy that’s done correctly, all your tonsil tissue should be removed, and the chance of the tissue returning is small. But there’s a challenge in removing them that can cause the rare cases of second-time-around tonsils.

“Your tonsils blend in with the back of your tongue at the very bottom part, and there’s not always a sharp distinction of where the tonsil ends,” says Dr. Richard Rosenfeld, chairman of otolaryngology at SUNY Medical Center, “So you could leave a little tissue there.”

For the past century, the process of removing tonsils has been pretty standard—just cutting them out. It used to be a popular procedure for kids who had frequent throat infections like strep, but in the past few decades, that practice has waned. Today, tonsillectomies are usually reserved for patients with tonsils big enough to interfere with their breathing.

In the early 2000s, the practice changed in some parts of the US as a partial tonsillectomy procedure became popular. Some surgeons now just trim tonsil tissue instead of attempting to completely remove it. It’s suggested that this technique could ease the recovery process, though there’s no consensus among throat doctors on this point. The downside of the procedure is that purposefully leaving behind part of the tonsils makes it easier for the leftover tissue to regenerate into your trusty old tonsils.

Before you worry too much about your tonsils making a comeback, know that it’s relatively uncommon, and it might be more likely to happen when tonsils are removed in children whose lymphoid tissues are still growing. Out of the thousands of tonsillectomies he’s done, Rosenfeld says only one patient has returned with a new set of tonsils.

On the other hand, adenoids, the lymphatic tissues between your nose and the back of the throat, are often removed at the same time as tonsils. They can also grow back through regenerating tissue, and they do so more frequently than tonsils. Adenoids are spread out across your nasal cavity, and surgeons can’t remove them all, so they can grow and spread from the tissues left behind.

However small the chance, know that just because your tonsils are out doesn’t mean they’re gone forever. If you’re curious whether yours have returned, just open your mouth and look in the mirror—you should be able to see them if they’ve grown back close to their original size.