Invasive/Infiltrating Ductal Carcinoma (IDC)

by PJ Hamel Patient Expert

Expert Patient PJ Hamel takes you through the basics of Invasive or Infiltrating Ductal Carcinoma, from what IDC is to what treatment to expect.

Q. I've learned I have IDC, which the doctor called infiltrating ductal carcinoma. But someone else called it invasive ductal carcinoma. Are they the same thing?

A. Yes, they are. And here's what's going on: atypical cells-cells that, for an unknown reason, mutated as they grew-have collected in the ducts in your breast. Ducts are the tiny tubes that carry milk from the lobules, where it's made, to the nipple. At some point, these atypical cells broke through the duct wall, and started moving into the surrounding tissue. This is when your cancer crossed the line from DCIS-ductal carcinoma in situ-to invasive (infiltrating) ductal carcinoma-IDC.

Q. So what suddenly made these cells move into the rest of my breast, rather than just continue to collect?

A. Excellent question. And researchers would love to know the answer: if they knew WHY cells suddenly start to move and migrate, they might be able to figure out how to stop them. Right now, their best guess is not that the cells themselves suddenly became more aggressive, but that that something around the cells-a hormone, other cells-gave them the "go ahead" to move. But that's still a theory; research continues.

Q. How many women get this particular type of breast cancer? Is it one of the common ones?

A. Yes. In fact, infiltrating or invasive ductal carcinoma is the most common type of breast cancer; 70% of women with breast cancer have this diagnosis. And 80% of women with invasive breast cancer have IDC. So you've got lots of company.

Q. What will my treatment be like for infiltrating/invasive ductal carcinoma?

A. While some breast cancer is difficult to detect, IDC is fairly straightforward: it's characterized by a lump in the breast, which is probably what caused you to call the doctor in the first place. This lump, made up of cancerous cells surrounded by scar tissue caused by the cancer, is what the radiation oncologist took a sample of-a biopsy-to see if it contained cancer cells. In your case, it did.

Next step is to get rid of that lump (and thus most or all of the cancer cells). Depending on a number of factors (including size; whether any other lumps have been detected, and the various ways the pathologist interpreted your particular cancerous cells), you may have a lumpectomy, where just the lump and some surrounding tissue is removed; or a mastectomy, where all of the breast tissue in that breast is removed. If you have a lumpectomy, it'll probably be followed by radiation to kill any leftover cancer cells in your breast. And if lymph nodes are involved you may be advised to have chemotherapy, as well. Depending on your age and the biology of your cancer, chemotherapy is sometimes recommended even if the lymph nodes are not involved.

Editor's Note: Also check out our special section on treatment options for infiltrating/invasive ductal carcinoma, with advice from survivors and physicians.

Q. How do I decide whether to have a lumpectomy or a mastectomy? Do I make that choice, or will the doctor tell me what to do

A. Lumpectomy vs. mastectomy is one of the toughest decisions a woman with breast cancer has to make (if she's given the opportunity for that decision). Some women, no matter how small the lump, decide they can't stand the thought of cancer in their breast, and would just as soon get rid of the breast than continue to worry about it. Other women prefer the less invasive lumpectomy procedure, trusting and hoping that between that and radiation, the cancer will be killed.

Will your doctor tell you what to do? Probably not. Unless it's very clear that you need a mastectomy, the doctor will leave it up to you to decide-which can be scary and frustrating! See if your hospital or cancer center offers help with making health decisions: something along the lines of a "shared decision making" center, where professionals are trained to help you make just this kind of tough decision. If so, access that resource-I guarantee it'll be helpful.

Q. How can they tell if the cancer has spread to my lymph nodes?

A. When you have surgery (either lumpectomy, or mastectomy), one or more lymph nodes in your armpit-the first place cancerous cells from the breast would travel-will be removed, examined, and labeled positive (cancer cells), or negative (no cancer cells). Even one positive lymph node is a sign that the cancer is starting to advance, and the signal that your treatment will probably be more extensive.

Q. Will I need to take any long-term drugs, once I've finished the initial treatment?

A. You may take tamoxifen (Nolvadex), Herceptin, or an aromatase inhibitor (Arimidex, Femara), depending on whether or not your particular cancer is hormone-receptive; that's something the pathologist will have determined, and you doctor will tell you. The majority of women with breast cancer do have hormone-receptive cancer, so yes, odds are you'll be taking drugs for at least several years after you're through with surgery and whatever other treatment your doctor deems necessary.

Good luck with all of this-remember, you're not alone. Millions of women have gone through cancer treatment, particularly treatment for infiltrating/invasive ductal carcinoma, and come out on the other side to happily resume their lives. One of the good things about cancer is that you'll probably make great new friends during treatment. You'll walk down this path together, and be all the stronger for having done it.

PJ Hamel
Meet Our Writer
PJ Hamel

PJ Hamel is senior digital content editor and food writer at King Arthur Flour, and a James Beard award-winning author. A 16-year breast cancer survivor, her passion is helping women through this devastating disease. She manages a large and active online survivor support network based at her local hospital and shares her wisdom and experience with the greater community via