Lobular breast cancer, also called invasive lobular carcinoma (ILC), occurs in the breast lobes, called lobules. Lobules are the areas of the breast that produce milk. ILC is the second most common type of breast cancer.

ILC affects about 10 percent of people with invasive breast cancer. Most people with breast cancer have it in their ducts, which are the structures that carry milk. This type of cancer is called invasive ductal carcinoma (IDC).

The word “invasive” means that cancer has spread to other areas from the point of origin. In the case of ILC, the starting point is a particular breast lobule.

For some people, the cancerous cells have spread to other sections of the breast tissue. For others, the disease has spread (metastasized) to other parts of the body.

Your prognosis will depend on many factors, including the grade and stage of your cancer, as well as your long-term care plans. Follow-up appointments and tests can help your doctor detect a recurrence of cancer or any other complications.

Like other cancers, ILC is staged on a 0 to 4 scale. Staging has to do with the size of the tumors, lymph node involvement, and whether tumors have spread to other areas of the body. Higher numbers represent more advanced stages.

Research shows that ILC often has a good prognosis because the cancer cells are generally low grade, and they respond well to hormone treatment.

This responsiveness to treatment is favorable to your prognosis. Most of these types of cancers are hormone receptor-positive, usually estrogen (ER) positive. This means the cancer cells must have the hormone to grow. So medication that blocks the effects of estrogen can help prevent a return of disease and improve your prognosis.

But ILC tumors can often spread aggressively. People diagnosed with ILC are on average 3 years older at diagnosis compared with those with IDC. ILC is also most often diagnosed at a more advanced stage.

Several studies demonstrate that the overall long-term outcome for people diagnosed with ILC may be similar to those diagnosed with other types of invasive breast cancer. Some subgroups of people with ILC have worse outcomes than IDC, primarily related to the type of tumor they have and its treatment.

If you’ve been treated for ILC, it’s especially important to schedule a physical exam and a mammogram every year after your treatment. The first one should take place 6 months after surgery or radiation therapy is complete.

Survival rates for cancer are typically calculated in terms of how many people live at least 5 years after their diagnosis. The average 5-year survival rate for breast cancer is 90 percent, and the 10-year survival rate is 83 percent. This is an average of all stages and grades.

The stage of the cancer is important when considering survival rates. For instance, if the cancer is only in the breast, the 5-year rate of survival is 99 percent. If it has spread to the lymph nodes, the rate decreases to 85 percent.

Because there are many variables based on the type and spread of cancer, it’s best to talk with your doctor about what to expect.

Lobular breast cancer sometimes begins without symptoms. It may show as an abnormal area on a mammogram, which leads to further examination.

Spotting ILC on a mammogram can be difficult because the cancer cells spread in a line rather than in a distinctive lump, as in IDC. Magnetic resonance imaging (MRI) imaging is reported to provide more sensitive images that may show the cancer better.

The first symptom of ILC is sometimes a thickening or hardening of a portion of the breast. This thickening can be felt by touch, but it feels different from the classic lump associated with IDC, the more common breast cancer.

Other symptoms of ILC may include:

  • swelling or fullness in a part of the breast, or in the whole breast
  • a change in the skin texture in a part of the breast
  • dimpling in the breast
  • a nipple that turns inward
  • pain in the breast or nipple

The exact cause of ILC is currently unknown. But there are some risk factors that are associated with ILC. These can include:

  • being female
  • older age
  • taking hormone replacements, for menopause for example

Although people can be diagnosed with lobular breast cancer at any age, it’s most common in women ages 55 years and older. Research suggests that hormone replacement therapy after menopause, especially with progesterone, may increase the risk of this type of cancer.

The word “invasive” in the ILC name means that the cancer has spread. It may have spread to breast tissues surrounding the lobules where it began or beyond that to other organs of the body. If the cancer cells have not yet spread, the cancer is referred to as lobular carcinoma in situ (LCIS).

Over time, ILC can spread to lymph nodes and to further parts of the body. When ILC does spread to other organs, doctors call this metastasizing. It most commonly spreads to:

  • bone
  • uterus
  • ovary
  • stomach
  • brain
  • liver
  • lungs

It’s important to understand the difference between the stage and the grade numbers assigned during a cancer diagnosis. The cancer’s stage refers to its size and how much it has spread. Grade is a measure of the cancerous cells — appearance and predicted tendency to spread.

Specifically, grade refers to how similar or different your cancer cells are to a normal cell. This grade will be noted after your cancer cells have been examined under a microscope. This will require a biopsy. You’ll probably see an assigned grade of 1, 2, or 3.

The lowest — grade 1 — refers to cancer cells that resemble normal breast cells, are slow-growing, and least likely to spread. Grade 2 cells look less like normal cells and are growing a bit faster. Grade 3 cells look much different and will likely grow and spread the fastest.

The grade number assigned to your cancer will help your doctor decide on the best course of treatment for you and gauge your prognosis.

The earlier you’re diagnosed with ILC and start treatment, the better your outlook. As with other types of cancer, early stages of ILC are likely to be treated more easily with fewer complications. This typically — but not always — leads to a complete recovery and low recurrence rates.

But compared with the much more common IDC, early diagnosis of ILC can be a challenge. That’s because the growth and spread patterns of ILC are more difficult to detect on routine mammograms and breast exams. ILC tumors are likely to have multiple origins, and they grow in single-file lines rather than a lump.

The first step in a diagnosis of ILC is a breast examination. Your doctor will feel your breast for a thickening or hardening of the tissue. They’ll also look for any swelling in the lymph nodes under your arms or around your collarbone.

Other diagnostic tests may include:

  • Mammogram. These tests produce X-rays of the breast. Both breasts will be X-rayed. Several images may be taken to focus on areas of concern.
  • Ultrasound. This test bounces sound waves off the breast to give further views of the breast. Ultrasound sometimes provides more accurate images of ILC than a mammogram, but the two tests are usually used in combination.
  • Breast MRI. An MRI uses magnetic waves to produce images of the breast tissue, which are sometimes the most sensitive views for ILC.
  • Biopsy. When imaging suggests the possibility of ILC, your doctor will do a biopsy to examine the tissue itself. This involves extracting some or all of the possibly cancerous tissue, which will be evaluated by a pathologist.

The classic, or most common, ILC cells are small. They spread through the breast tissue one by one, in line formation, sometimes branching out like the limbs of a tree. The cells tend to look alike, and they have small nuclei that resemble each other.

Beyond the classic ILC cells, there are also subtypes of ILC cells. These cells do not form in this single-file pattern, which can be seen under a microscope. These subtypes can include:

  • Solid: These cells form in large sheet formations, instead of the single-file lines of classic cell formation.
  • Alveolar: These ILC cells grow in groups of 20 or more, rather than singly as the classic cells do.
  • Tubulolobular: These cells form in small tube-like structures, in addition to the single-file structure seen in classic ILC cells.

There are additional ILC subtypes whose cells do not look like the classic ILC cancer cells. These subtypes include:

  • Pleomorphic: These cancer cells are larger than the classic type, and their nuclei do not resemble each other.
  • Signet ring cell: These cells are filled with mucus and have a shape that resembles a signet ring.

ILC can be more difficult to diagnose than other forms of breast cancer because it spreads in a unique pattern that’s not always noticeable in imaging tests. The good news is that it’s a relatively slow-growing cancer, which gives you time to form a treatment plan with your cancer team.

There are several treatment options that can help increase your chances of a full recovery.


Treatment varies depending on the stage of your cancer. Small tumors in the breast that have not yet spread may be removed in a lumpectomy. This procedure is a scaled-down version of a full mastectomy. In a lumpectomy, only part of the breast tissue is removed.

In a mastectomy, an entire breast is removed with or without the underlying muscle and connective tissue.

Other therapies

Hormonal therapy, also called anti-estrogen therapy, or chemotherapy may be used to shrink tumors before surgery. You may need radiation after a lumpectomy to make sure all of the cancer cells have been destroyed.

Your doctor will help you form a care plan that’s personalized based on your health, using the most current technologies available.

A diagnosis of ILC can be challenging because it’s difficult to see on imaging tests, and it hasn’t been as well-studied as the more common ductal breast cancer called IDC. But after diagnosis, treatment is available and the 5-year survival rates are encouraging, especially when caught early.

Prognoses vary, depending on the grade and stage of the cancer. The good news is that ILC tends to be slow-growing and responsive to hormonal treatment. But it also tends to metastasize aggressively, so early detection is important.

The best path to early detection involves regular mammograms and reporting any changes you notice in your breasts to your doctor immediately.

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