Lobular carcinoma in situ (LCIS) arises within the milk glands, while ductal carcinoma in situ (DCIS) arises within the milk ducts of the breast. Both of these diagnoses represent abnormal, even cancerous, cells that remain contained within their structure of origin. They are most commonly diagnosed as incidental findings on screening mammography, identified by characteristic patterns of breast calcifications.

Numerous pathology and epidemiology studies suggest that there is far more LCIS and DCIS than ever develop into invasive breast cancer. Thus not all LCIS or DCIS should need aggressive management. However, we still don’t have sufficiently robust markers to distinguish the in situ cancers that will evolve, from those that will not.

LCIS used to be considered a true cancer, but now most LCIS is recognized as a non-malignant entity that is mainly a marker of risk, rather than cancer itself. A diagnosis of LCIS suggests an increased likelihood of real breast cancer developing in the same or opposite breast.

The risk of breast cancer after LCIS is several-fold higher than that of the general population. Cancer registry data suggest that there is an 11% risk at 10 years and a nearly 20% risk at 20 years, with about 55% of new cancers in the same breast, but up to 45% of subsequent cancers in the opposite breast.

For most patient with LCIS, surgery is only indicated for biopsy. Complete excisions not necessary. Rather, these patients should be entered in to high-risk surveillance programs and offered chemoprevention interventions that prevent estrogen stimulated tumor development.

A rare form of LCIS, known as pleomorphic LCIS, is more frequently associated with adjacent DCIS or even invasive disease. This pleomorphic LCIS should not just be needle-biopsied, but should be removed with adequate tissue to detect adjacent more worrisome cancers.

DCIS, on the other hand, IS true cancer that is confined to the milk ducts. This disease may evolve into invasive ductal cancer. If inadequately treated, recurrence is associated with recurrence as invasive ductal cancer about 50% of the time. Although DCIS itself, poses no immediate life-threat, it’s ability to recur as invasive disease suggests the potential of a life-threatening risk.

For these reasons, the goal of DCIS treatment is complete surgical removal, in some cases coupled with other modalities, such as radiation or drug therapy, that minimize chance of recurrence. Surgical removal may be via lumpectomy, with breast preservation, or through total mastectomy.

Although most DCIS is localized, and suitable for breast conservation surgery, DCIS presents a unique challenge; the disease often extends along ducts over a significant distance. Furthermore, some DCIS appears as so-called skip-lesions, in which multiple areas of DCIS may be separated by apparently uninvolved breast tissue. This may be referred to as multi-focal or multi-centric disease.It is when these features are present that a recommendation for mastectomy is often made.

Because of the growth characteristics of DCIS, it is difficult to identify the clear edge of an area of tumor. Preoperative size estimates are usually based on extent of characteristic calcifications, but the disease may extend beyond the calcifications. Thus, occasionally, after lumpectomy surgery, extensive involvement of margins of resection can lead to recommendation for further surgical intervention. Oncoplastic surgery approaches, which provide a broader access, and more generous tissue removal, while still preserving the cosmetic appearance of the breast, can be particularly useful in this setting.

When resection is clear, and when there is no evidence of other suspicious foci, patients with suitable tumor biology may be able to avoid the radiation therapy most commonly recommended to patients as “standard-of-care”. Gene expression profiling may identify tumors with low risk biology, in which recurrence as invasive cancer is very low. In some cases the risk of invasive recurrence may equal the risk of new invasive cancer on the opposite uninvolved side. For these patients, radiation therapy has little to add, beyond cost and toxicity.

LCIS and DCIS pose challenges in management that go well beyond “cutting out a lump”. An experienced breast surgical oncologist, has the training, background, and experience to manage these challenging diseases.