What is invasive lobular carcinoma (ILC)?

Invasive lobular carcinoma (ILC) accounts for about 10% of all invasive breast cancers . Lobular indicates the origin: this cancer begins in the milk-producing lobules of the breast.

In lobular carcinoma in situ , the abnormal cells are confined inside the lobule. Having LCIS in one breast increases the risk of developing breast cancer in either breast: “compared to the general population, women with LCIS have an eight-fold to ten-fold increased risk of breast cancer.”

Once-upon-a-time, doctors recommended mastectomy when a pathology report yielded LCIS, but with no discernible difference in outcomes (mortality), this recommendation was tabled. From 2011, when I started my journey.

Today, a diagnosis of LCIS remains one of the greatest identifiable risk factors for the subsequent development of breast cancer. As such, patients are offered one of three options: (1) lifelong surveillance with the goal of detecting subsequent malignancy at an early stage; (2) chemoprevention; or (3) bilateral prophylactic mastectomy…

When LCIS was first described, it was treated as a malignancy necessitating mastectomy, like all breast carcinomas at the time. This remained the standard approach until studies demonstrated that the actual risk of breast cancer was lower than expected and that women with LCIS were equally likely to be diagnosed with contralateral as with ipsilateral breast cancer, leading to the conclusion that bilateral total mastectomy would be the only logical operation that could truly reduce risk. In parallel with the trend toward more conservative therapy for the treatment of invasive breast cancer, aggressive surgical therapy for LCIS fell out of favor, and in our experience, only a minority of women with LCIS (5%) will pursue bilateral prophylactic mastectomy (BPM). Nevertheless, BPM may be a reasonable option for a subset of women with LCIS and other risk factors, such as a strong family history or extremely dense breasts.

I am in the subset of “extremely dense breasts.”

In my case, it would have been a smart thing to have undergone a mastectomy six years ago. However, I do not recall its being discussed as an option, even one that has been subsequently tabled. Moreover, based on my contemporaneous notes, I left my consultation with the oncologist far more concerned about atypical ductal hyperplasia than LCIS.

We did discuss tamoxifen, however subsequent research shows that ILC is not particularly responsive to tamoxifen relative to other hormonal therapies.


Invasive lobular carcinoma (ILC) differs from LCIS in that the cancer cells have escaped the walls of the lobule. ILC is difficult to see on a mammogram because the cells line up single-file, instead of forming a mass. In my case, the ILC did not show up on MRIs, either, even after having been found by accident in a mammogram-triggered biopsy. [For the past six years, I was scanned two times a year, both mammogram and MRI.]

ILC tends to be a slow-growing cancer when compared with invasive ductal carcinoma.

Invasive lobular carcinoma is slow to spread outside the breast. If it does, it tends to show up in the gastrointestinal tract (which includes organs such as the stomach and intestines), the lining of the abdomen, or reproductive organs such as the ovaries. It also may spread to the tissues that cover the brain and spinal cord.

Because my cancer is slow growing but has spread to lymph nodes, we know that it has been hanging around a long time.


See ILC research.