Lobular breast 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, the most common type. Lobular breast cancer is also more likely to have a hereditary component. Palpable lobular tumors (i.e., those that can be felt by hand even if only as a firmer area) are associated with higher tumor grade and worse overall survival than nonpalpable lobular tumors.
Women with lobular carcinoma in situ (LCIS), also known as lobular neoplasia, are at higher than average risk for invasive breast cancer, but the risk is higher for developing ductal as well as lobular breast cancer. One 2017 study reported that the seven-year cumulative invasive breast cancer incidence was 9.9% after an initial diagnosis of atypical hyperplasia or LCIS. Efforts to predict which LCIS patients will progress to invasive breast cancer have so far been unsuccessful.
Use of hormone replacement therapy (HRT) containing both estrogen and progestin 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. Although still rare, women with lobular breast cancer are more likely to get ovarian and gastric (stomach) metastases than those with other types of breast cancer. While lobular breast cancer may have indolent, non-aggressive characteristics compared to ductal breast cancer and other types, both the primary tumor in the breast and distant metastases can be difficult to detect. As a result, long-term prognosis is not superior to that of ductal breast cancer.
Lymph node micrometastases in lobular breast cancer
As is the case for other types of breast cancer, lobular breast cancer patients with positive lymph nodes have worse prognosis than those with clear lymph nodes. However, the significance of lymph node micrometastases appears to differ.
Micrometastases include metastases of 2 mm or less, tiny cell clusters, and isolated tumor cells. Generally speaking, micrometastases in lymph nodes have not been found to significantly influence breast cancer prognosis. For example, one study found that undetected micrometastases influence prognosis in patients with sentinel lymph nodes that are initially classified as negative, but the magnitude of the difference in outcome at five years was only 1.2%. Since identifying such micrometastases requires more intensified pathological assessment of lymph nodes, these study findings could result in less use of techniques to find micrometastases (metastases which would otherwise remain occult or undetected). However, because of the diffuse nature of lobular breast cancer, lymph node metastases are more likely to be micrometastases than in ductal breast cancer. Forgoing pathological techniques that could find otherwise undetectible micrometastases in lobular breast cancer cases might cause some tumors to be incorrectly staged.
Multifocal and contralateral tumors
As noted above, lobular breast cancer is more likely to be multifocal or multicentric (more than one tumor per breast) and bilateral (diagnosed in both breasts) than other breast cancer types. While five-year survival rates are similar, ten-year survival rates are lower for multifocal breast cancer. In addition, five-year survival rates are lower for women with contralateral breast cancer compared to those with tumors only in one breast. This appears to be because bilateral breast tumors tend to have more aggressive characteristics. Lobular breast cancer patients should receive MRIs of both breasts before surgery to identify all tumors. The higher possibility of undetected lesions in lobular breast cancer argues for systemic treatment in addition to lumpectomy and radiation even for relatively small lobular tumors.
Other factors associated with recurrence
One large Swedish study, which followed women with lobular breast cancer for over 20 years, reported that positive lymph node status, high proliferation (defined as Ki-67 ≥ 30%), and significant tumor size (≥ 20 mm) each were associated with recurrence. On the other hand, lobular breast cancer patients with clear lymph nodes, low proliferation and small tumor size had the most favorable long-term outcomes, with a breast cancer mortality rate of 12% after 20 years.
We have elected not to try to summarize the statistics concerning risk of recurrence for lobular breast cancer here because it varies greatly depending on numerous factors. Specific data concerning relapse and survival can be found in the studies below.
Below are links to recent studies on this topic. For a more complete list of studies, please click on lobular breast cancer. Please also see our articles on lobular breast cancer (which describes this type of breast cancer) and diet for lobular breast cancer patients and survivors.