Up to 15 percent of U.S. invasive breast cancers are classified as lobular, which refers to the fact that the cancer developed in the cells that line the milk-producing glands (lobules) of the breast. The most common histological type of breast cancer, accounting for approximately 70 percent of cases, is ductal breast cancer, which forms in the milk ducts. Lobular cancer is more likely to be multifocal (more than one tumor per breast), bilateral (diagnosed in both breasts at the same time), and both estrogen receptor-positive and progesterone receptor-positive (ER+/PR+) than ductal breast cancer, and it is also more likely to have a hereditary component. In fact, lobular breast cancer patients are more likely to have a father diagnosed with cancer, especially prostate cancer.

It is rare for lobular breast cancer to be HER2 positive. Almost half of women diagnosed with lobular breast cancer are treated with mastectomy, either initially or after a lumpectomy that does not result in clean clean margins. Women with lobular carcinoma in situ (LCIS) (also known as lobular neoplasia) or atypical lobular hyperplasia (a possible precursor of both LCIS and invasive breast cancer) are at higher than average risk for invasive breast cancer, but the risk is higher for developing ductal as well as lobular breast cancer.

Use of hormone replacement therapy (HRT) containing both estrogen and progesterone has been shown to increase the risk of invasive lobular breast cancer. Being overweight also increases the risk of lobular breast cancer and recurrence after menopause. Women with lobular breast cancer are more likely to get ovarian and gastric (stomach) metastases than those with other types of breast cancer. Please see our article on what lobular breast cancer patients and survivors should eat for information pertaining to diet and supplements. We suggest that LCIS and lobular breast cancer patients and survivors also refer to the articles that discuss their individual breast cancer subtypes (e.g., ER+/PR+, ER+/PR-, triple negative).

Risk of progression from LCIS to invasive breast cancer

Efforts to predict which LCIS patients will progress to invasive breast cancer have not been very successful. However, one 2012 study reported that LCIS with high Ki-67 (a marker of proliferation) expression is more likely to progress to invasive breast cancer than low Ki-67.

Since the majority of women with LCIS do not go on to develop invasive breast cancer, some do not undergo surgery to remove the LCIS lesion. Rather, they are placed under increased surveillance and they may receive endocrine treatments. However, since a substantial minority of women diagnosed with LCIS based on core needle biopsy are found to have invasive breast cancer upon open surgical biopsy, many experts are of the opinion that surgical biopsy should follow needle biospy to confirm that the diagnosis is limited to noninvasive breast cancer. It is also important for women who do progress to invasive breast cancer to have all of their LCIS surgically removed.

The picture is more clear for pleomorphic lobular carcinoma in situ (PLIS), a more high-risk type of LCIS. When patients are diagnosed with PLCIS using a needle biopsy, the lesion should be surgically removed. In addition, re-excision should be performed if any PLCIS or LCIS is found at or near the surgical margins.

Diagnosing lobular breast cancer

Lobular breast cancer is less visible on mammograms, sonograms and MRIs than ductal beast cancer because the cancer cells infiltrate between normal cells in a very regular manner. Typically, it does not form a lump. Instead, the breast may feel thicker or more firm in the area of the tumor. Because of these factors, lobular breast cancer often is diagnosed when it has reached a larger diameter than other types of breast cancer. Nevertheless, because this type of breast cancer typically does not behave aggressively, lobular breast cancer patients tend to have a relatively good prognosis despite the larger tumor size at diagnosis.

On the other hand, lobular breast cancer that is palpable (i.e., can be detected manually) is associated with higher tumor grade and poorer survival than lobular cancer that cannot be felt by hand. Also, lobular breast cancer can relapse many years after initial diagnosis and treatment.