Like ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS) is not classified as invasive breast cancer. In DCIS, the cancer cells have not spread beyond the duct walls to invade the surrounding tissue, whereas in LCIS the cells have not spread beyond the milk-producing glands (lobules) of the breast. However, DCIS has greater potential to lead to invasive breast cancer than LCIS. If left untreated, at least a third of DCIS cases will progress to invasive breast cancer whereas approximately one-fifth of LCIS patients will eventually develop invasive breast cancer.

Also, while DCIS is a direct precursor to ductal breast cancer, women with LCIS can go on to develop lobular or ductal breast cancer and this may occur in the contralateral (opposite) breast, suggesting that LCIS is not a direct precursor to invasive breast cancer. In addition, this condition is rare—LCIS is found in fewer than 2% of all breast cancers. These factors have led to a great deal of variability in the management of LCIS, from increased surveillance to mastectomy. Now a new study has reported that recurrence rates for LCIS are significant, especially among women who are treated with lumpectomy without radiotherapy.

When does LCIS lead to invasive breast cancer?

While it is not possible to predict which LCIS patients will develop invasive breast cancer, there are some factors known to make it more likely. It is important that these variables be considered in deciding how to treat LCIS.

  • Palpable LCIS. Note that LCIS that can be detected manually is more likely to feel like an area of thickening or firmness than a lump.
  • High Ki-67 expression. Ki-67 is a marker of proliferation that normally can be found in breast cancer pathology reports.
  • Pleomorphic LCIS. Such lesions should be removed surgically when diagnosed with a needle biopsy.
  • Cigarette smoking is associated with increased risk of invasive breast cancer in women with LCIS.
A substantial minority of women diagnosed with LCIS based on core needle biopsy will be found to have invasive breast cancer upon open surgical removal of the tumor. One study reported that 27% of tumors with LCIS found in core needle biopsy also contained invasive breast cancer. This has led some experts to recommend that surgical biopsy should follow needle biopsy to confirm that the diagnosis is limited to LCIS. The treatment decision is then based on whether invasive breast cancer was also found.

Note that atypical lobular hyperplasia, which appears to be a precursor to both LCIS and invasive breast cancer, is more likely to progress to invasive breast cancer than LCIS.

Latest research finds LCIS is not always an indolent disease

The retrospective study referenced at the beginning of this news story was designed to investigate LCIS outcomes. The study included 200 women (median age 52) with pure LCIS who were treated in seven centers between 1990 and 2008. A total of 176 (88%) of the study participants underwent breast conserving surgery (typically, lumpectomy) and 24 (12%) had a mastectomy. Seventeen of the women received whole breast radiotherapy after breast conserving surgery. Fifteen of the women were also treated with tamoxifen and five received an aromatase inhibitor.

None of the 24 women who underwent a mastectomy experienced a local breast cancer recurrence (i.e., in the same breast, chest wall, or lymph nodes) during follow up. Three late local recurrences (i.e., after 10 years) occurred among the 17 women treated by breast conserving surgery plus whole breast irradiation. Among the 159 patients treated with breast conserving surgery without radiation, 20 (13%) experienced a local recurrence within 72 months and 17.5% experienced such a recurrence within 10 years. The authors were not able to identify specific risk factors associated with local recurrence.

Three of the 200 study participants developed distant metastases during follow up: two after first experiencing invasive local recurrence. A total of 22 (11%) of the women developed breast cancer in the contralateral breast—59% of these tumors were invasive. An additional five of the women were diagnosed with a second cancer during follow up. The authors conclude that LCIS is not always an indolent disease. The long-term outcome is quite similar to DCIS, according to the authors, who conclude that more accurate pathological definitions and clear identification of more aggressive subtypes are needed. Furthermore, breast conserving surgery plus whole breast irradiation makes sense in some selected cases, and the long-term results of such treatment appear comparable to DCIS.

Please see our article on lobular breast cancer and LCIS for more information.