Breast cancer is the second most common form of cancer (next to skin cancer) for women in America … and carries the second highest cancer death rate (next to lung cancer).

Odds, sadly, are very good that you or someone you know has had a scare, sickness, or untimely death due to this pernicious killer.

But fear doesn’t always lead to the best medicine. Indeed, when it comes to breast cancer, some of the things we’re doing may cause more harm than good.

And a new study published in the Journal of the American Medical Association (JAMA) just highlighted one of the most common overtreatments we suffer from — and why it is so dangerous.

Sometimes a lesion is just a lesion

Today, 20 percent of all new breast cancer cases aren’t actually cancer at all. They are lesions called ductal carcinoma in situ, or DCIS for short. These lesions can lead to breast cancer. But there’s no clear evidence as to how often that happens.

Yet, until recently, every case of DCIS was going under the knife. And that should worry you.

In the new study, researchers found that it’s not the DCIS that matters — it’s the cells that make up these lesions. Specifically, pathologists looked at the cells of more than 57,000 women who had DCIS. Most had surgery, while only a small percentage didn’t.

Ten years out, those with low-risk pathologies had absolutely no difference in survival rate, whether they had the surgery or not.

There was a slight difference if you had intermediate-grade risk cells: 98.6 percent of those who had the surgery survived breast cancer 10 years out, compared with 94.6 percent of those who didn’t have the surgery.

The gap grows when you look at high-risk cells: 98.4 percent of those who had surgery survived breast cancer after 10 years, compared with only 90.4 percent of those who didn’t.

So it’s clear that the riskier the DCIS cells, the bigger the difference pre-emptive surgery makes.

Or at least that’s the initial conclusion. Because, during the time period examined, surgery was always recommended, we aren’t dealing with controlled groups. Those who didn’t receive the surgery usually skipped it due to frail health, making them much more susceptible to problems later.

So the gap may not be as big as advertised.

But still — if getting a lumpectomy or mastectomy early leads to over 98 percent survival, we all should do it, right? Not so fast. It’s worth bearing in mind, the surgery itself carries risk.

Of course, there’s the general risk associated with anesthesia and going under the knife. But surgery also weakens your systems for an extended period of time. The trauma of surgery can have a cascade effect.

And a botched surgery can do more harm than good. If a lumpectomy doesn’t get all the pre-cancerous cells, it can actually spread them around during all that cutting, seeding the abnormal cells much farther and wider than if you’d done nothing.

And that’s to say nothing of other forms of treatment. Both radiation and chemo cause cell damage that can lead to cancer! They should never be attempted until necessary—but some doctors recommend them anyway.

Cautious observation, followed by swift action

So what’s the best way to handle DCIS? Know exactly what you’re dealing with, and go from there.

I had one 37-year old patient who came to me for a pre-surgery screening. She had DCIS, and her physician recommended cutting it out. I wanted to know if she was at risk. But her pathologist didn’t even know! The truth is, we don’t do a very good job of screening DCIS cells, in most cases.

On the other hand, I had a different patient who presented with some worrying blood markers. I told her to get checked out, but she put it off. A year later, she had full-blown cancer.

So what should you do if you have a DCIS?

First, get as many preliminary tests done as possible. There are blood markers that can indicate pathology, if not point directly to cancer. Read in context with a DCIS, good doctors can draw reasonable conclusions of danger.

Second, get more than one opinion. Leaving a high-risk DCIS in place isn’t the solution. But neither is treating a benign growth. More and more women are getting biopsies and insisting on an individualized study. They aren’t immediately leaping to surgery.

That’s the right thing to do. In most cases, vigilance is required first. After that, you can leap to surgery if necessary.

And third, take a good long breath. Remember, even with those women who had the most virulent cells and did nothing, over 90% survived. In all other cases, an even higher percentage made it out fine.

If you do have a virulent pathology, you should do something preemptive. But don’t panic, overreact, or over-treat.

Automatically reaching for the scalpel can do more harm than good.