Lobular carcinoma in situ is an rare finding without the presence of other disease. Rarely, it may be found on a breast biopsy by itself. This leads to two distinct clinical scenarios: LCIS in combination with other disease, or LCIS alone. Atypical lobular hyperplasia is usually considered in combination with LCIS.

LCIS Alone

LCIS is usually seen in pre-menopausal women. The most important implication of a diagnosis of LCIS is the increased risk of breast cancer that it conveys.

Historical treatment

LCIS was only recognised as an entity in 1941; it was initially treated (like most other breast malignancies of the time) with radical mastectomy. Due to frequent bilateral occurrence (up to 35%) some centres advocated bilateral mastectomies for the condition. This was called into question as the low rates of local recurrence following wide local excision were reported.

Modern Therapy

Modern treatment has been guided by the recognition that LCIS itself rarely transformed into invasive disease, but rather served as an indicator for the future development of disease. The most important study regarding LCIS was the NSABP P1 prevention study (latest update in 2005); this showed that addition of tamoxifen reduced the incidence of future breast cancer by about 50% with 5-10 years follow up.
The two main approaches to the treatment of LCIS are:

  • Close observation and yearly mammograms for early detection of DCIS or invasive disease
  • Tamoxifen therapy in addition to the above for an added reduction of risk; albeit with an increase in thromboembolic events and endometrial cancers

LCIS in combination with additional diagnoses

When LCIS is found in association with another diagnosis, that other diagnosis dictates the course of management. LCIS does not require complete excision; it only increases the risk of further malignancy in the future.