Infiltrating/Invasive Lobular Cancer (ILC)

Patient Expert

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

Q. I've heard of women with DCIS and IDC, but I just found out I have ILC. What's that?

A. ILC-infiltrating lobular carcinoma-is similar to IDC (infiltrating ductal carcinoma), and the two are usually paired when you're reading about types of breast cancer. The main difference involves geography: IDC occurs in your breast's ducts, the tiny tubes that carry milk from where it's manufactured-in the lobules-to your nipple. ILC occurs in-you guessed it-those milk-manufacturing lobules.

Here's what's going on: atypical cells-cells that, for an unknown reason, mutated as they grew-have collected in the lobules in your breast. At some point, these atypical cells broke through the lobule wall, and started moving into the surrounding tissue. This is when your cancer crossed the line from LCIS-lobular carcinoma in situ-to invasive (infiltrating) lobular carcinoma-ILC.

While most breast cancer (86% of all breast cancer) occurs in the ducts, just 12% occurs in the lobules. So you can feel special... I guess! (I have ILC myself, and confess to a certain silly "pride" in going against the tide!)

Q. The weird thing was, while the doctor says the tumor might be as large as 2 centimeters, no one can feel it. It was picked up on a mammogram. How come there's no evident lump?

A. Lack of a palpable lump is another aspect of lobular cancer distinguishing it from ductal. When ductal cancer becomes invasive, it breaks through the duct walls and wreaks havoc in the surrounding breast tissue, creating all kinds of scar tissue; this scar tissue quickly becomes a hard lump, something you can feel. In ILC, however, the cancer cells are sneakier. Rather than break out in large groups, they tend to form long, skinny "fingers," which are much less irritating to healthy tissue. Thus you'll probably never feel a lump with ILC. In fact, what you WILL feel, when there are enough cancer cells, is a thickening, a kind of general texture change in the part of your breast with cancer. Obviously, since this kind of change is not nearly as straightforward as a lump, it's tougher to notice. The average ductal carcinoma is 2cm by the time you can feel it; the average lobular, 5cm. Big difference, huh?

Q. So, what might my treatment be?

A. Your treatment will be very similar to treatment for IDC. One difference might be in the surgery. Because ILC forms long chains of cancer, rather than a lump, it's usually more spread out, and thus more difficult to remove surgically. If you have a lumpectomy, it'll probably be tougher than usual to get clean margins-a margin of healthy breast tissue, all around the tumor(s), that tells the surgeon there's a good chance he or she has cut out all the cancer. You may go in for two lumpectomies, or even three, before you're "clean." And you may finally need to have a mastectomy, if the surgeon just can't find clean margins. So be prepared for a bit more uncertainty, going into the surgery phase of treatment. The remainder of your treatment-which might include radiation, chemotherapy, and long-term drugs-will be basically the same as IDC.

Q. Tell me more about the "sneaky" part. When I told one of my friends I have ILC, she said her mom had it and chose to have a double mastectomy, because they told her it's more difficult to diagnose, and there's more of a chance of ILC showing up in her other breast than with other kinds of breast cancer. Is that true?

A. It's true ILC is harder to diagnose than IDC; although with diagnostic tools improving all the time, the challenge is, thankfully, diminishing. And it's also true ILC is more likely to occur in both breasts than IDC. But the difference isn't huge: there's a 15% chance IDC will happen in both breasts, while with ILC it's 20%. Doctors did, in fact, in the past sometimes recommend a prophylactic (preventive) mastectomy of the unaffected breast for women with ILC; but this isn't a common recommendation anymore, particularly since treatment has become so much more effective.

Your best bet? Be vigilant. Have your regular mammogram and in between times, if your breast feels somehow different-remember, you'll most likely feel thickening, rather than a discrete lump-call your doctor.