Experts agree that early detection is the key to treating and beating breast cancer, but according to the New York Times, the diagnosis isn’t always right. Monica Long was diagnosed with ductal carcinoma in situ, or DCIS, the earliest stage of breast cancer, after they found a shadow of about one centimeter in her breast during her annual mammogram, and removed a golf-ball sized chunk of her breast. A year later, another doctor said her original diagnosis was wrong. She never had cancer and she endured surgery, radiation, and drugs for nothing.

What happened? Quite simply, Long was misdiagnosed. Unfortunately, it’s not uncommon. The breast cancer organization Susan G. Komen for the Cure released a study saying that in 90,000 cases, women who received a DCIS diagnosis didn’t have cancer. So why are all these women being misdiagnosed? It’s down to modern technology. Before the widespread use of mammograms in the 80s, people were rarely diagnosed with DCIS. Now, thanks to advances in technology, the lesions pathologists are seeing are tiny, some as small as a few grains of salt. Plus, they don’t always agree on what they’re seeing.

Dr. Shahala Masood is the head of pathology at the University of Florida College of Medicine. She says that diagnosing DCIS is a 30-year history of confusion, differences of opinion, and over-treatment. Also, there aren’t any mandated standards. That means the chances of getting a cancer diagnosis can vary from hospital to hospital. For example, at St. Mary’s Medical Center in San Francisco, breast lesions have to be over two millimeters to be considered for DCIS. However, Beth Israel Hospital in Boston will diagnose for much smaller lesions.

So what’s the fix? If you’ve gotten a diagnosis of DCIS, don’t rush to have surgery. One woman in the article was so scared; she immediately got a double mastectomy. Later, she found out she never had cancer at all. So definitely, get a second opinion. Dr. Michael Lagios is a pathologist who specializes in giving second opinions. He reviewed 600 cases in a two-year period, and found discrepancies in about 140 of them, including 30 cases where DCIS was misdiagnosed.