09/05/2012 02:06 pm ET

Invasive Ductal Carcinoma: Judy Blume's Breast Cancer, Explained

NEW YORK - NOVEMBER 8:  Author/activist Judy Blume attends the 15th Annual Glamour 'Women of the Year' Awards at the American
NEW YORK - NOVEMBER 8: Author/activist Judy Blume attends the 15th Annual Glamour 'Women of the Year' Awards at the American Museum of Natural History November 8, 2004 in New York City. (Photo by Evan Agostini/Getty Images)

Beloved author Judy Blume announced on her blog that she has undergone a mastectomy because of breast cancer.

People magazine reported that the "Are You There God? It's Me, Margaret" writer went in for a biopsy on June 12, which led to her diagnosis of invasive ductal carcinoma.

Very early. Very small. Well differentiated. All good news. But it was invasive ductal carcinoma. Wait – me? There’s no breast cancer in my family (recent extensive genetic testing shows no genetic connection). I haven’t eaten red meat in more than 30 years. I’ve never smoked, I exercise every day, forget alcohol - it’s bad for my reflux - I’ve been the same weight my whole adult life. How is this possible? Well, guess what – it’s possible.

Blume, 74, had a mastectomy on July 30 to remove the cancer, People reported.

Ductal carcinoma is the most common breast cancer, comprising 80 percent of breast cancer cases, according to Johns Hopkins Medicine. This particular type of breast cancer starts in the milk duct lining of the breast.

Blume's kind of cancer is invasive, meaning it had spread to other tissues and can spread even further throughout the body, the Mayo Clinic reported.

Other treatment options besides mastectomy for invasive ductal carcinoma include chemotherapy, radiation, lumpectomy and hormone therapy, according to Johns Hopkins Medicine. Treatments may depend on the stage and type of cancer.

As Blume noted on her blog, she didn't have many of the classic risk factors for breast cancer -- no family history as shown from genetic testing, a red meat-free diet, plenty of exercise, no alcohol, and no extreme weight gain. And as the American Cancer Society notes, having -- or not having -- a risk factor is not a guarantee that you will or will not develop cancer:

Having a risk factor, or even several, does not mean that you will get the disease. Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors (other than being a woman and growing older). Even when a woman with risk factors develops breast cancer, it is hard to know just how much these factors might have contributed.

However, breast cancer risk is known to go up with age, with women who are age 55 or older making up two out of every three invasive breast cancers cases, the American Cancer Society said.