It was cancer.
She's been free of the disease for 11 years now, and is CEO of the Susan G. Komen for the Cure, Greater New York City, which is engaged in the battle against breast cancer on numerous fronts.
October is Breast Cancer Awareness Month.
Some 182,000 women will be diagnosed with breast cancer this year, and it will claim 40,000 lives.
On The Early Show Wednesday, Richardson-Heron told co-anchor Julie Chen the breast cancer diagnosis "was very devastating for me. The first thing I did is what most people do: You act like it's not there. I was under the age of 40. And it's very unusual for women under the age of 40, typically, to get breast cancer, certainly 11 years ago. I have a family history of breast cancer. My mom had breast cancer. And, being a physician, I knew I had to be evaluated."
Her story, Chen pointed out, is similar to that of actress Christina Applegate, who had a double mastectomy. Her mother also had breast cancer.
How can women stay on guard against it?
"Fist of all," Richardson-Heron said, "it's very important to be aware of your breasts. We at Susan G. Komen make it very clear that you should be aware of your breasts. What that means is, touch your breasts. Know what they feel like. Know what's normal. And also, talk to your family about your family history of breast cancer. Back 26 years ago, before our organization was founded, many people didn't talk about breast cancer, so you didn't know if your mother or sister or another close relative had breast cancer. You should also talk to your doctor about the kind of screening tests that would be appropriate for you."
As far as that's concerned, Richardson-Heron said, "Right now, mammogram is the gold standard of care for people who are 40 and over and have an average risk of breast cancer. However, when you talk about people who are at higher risk, typically, you're thinking about people who have either the BRCA, BRCA one and two mutations, or people who have a high family risk, they may need additional tests, such as an MRI. But really, it's very important to talk to your doctor about the tests that are best for you."
There are "absolutely" lifestyle considerations women can incorporate into their lives that coudl reduce their risk, Richardson-Heron said: "One of the things that's important is to maintain a healthy weight. Obesity leads to an increase in estrogen in the body, and that's been thought to increase the risk of developing breast cancer. The other thing that it's very important for people to do is to make sure that you add exercise to your routine ... because exercise helps you maintain your weight as well. And also, avoid alcohol. There have been studies that have shown that increased alcohol results in an increased risk of breast cancer."
"It's important to note," Richardson-Heron stressed, "that a risk factor is just that. It increases your risks. It does not necessarily mean you will develop breast cancer."