Lobular carcinoma in situ (LCIS) is a noninvasive proliferative lesion of the breast that arises from the terminal ductal lobular units. It is typically asymptomatic; detected incidentally on core needle biopsy, most commonly in premenopausal women aged ∼ 50 years. Histologically, LCIS is divided into classic LCIS and LCIS variants, which include pleomorphic LCIS and florid LCIS. Although LCIS is a nonmalignant lesion, it is a risk factor for invasive breast cancer in the ipsilateral and contralateral breasts. Management is challenging, as the data on risk stratification of LCIS and the long-term benefits of treatment options are lacking. Treatment options include close clinical surveillance, surgical excision to rule out concurrent breast cancer, and prophylactic strategies such as chemotherapy or bilateral mastectomy to minimize the risk of developing breast cancer.
- Median age at diagnosis: 50 years 
- Approx. 85% of cases occur in premenopausal women.
- LCIS is a risk factor for invasive breast cancer.
Epidemiological data refers to the US, unless otherwise specified.
|Histological classification of LCIS |
|Classic LCIS (CLCIS)|
|LCIS variants ||Pleomorphic LCIS (PLCIS)|
|Florid LCIS (FLCIS)|
Quality evidence on risk stratification and optimal management of LCIS is lacking. Refer patients with LCIS to oncology. Shared-decision making is recommended when selecting a treatment strategy.
Close clinical surveillance 
- CBE every 6–12 months
- Women ≥ 30 years 
Surgical excision (breast conservation surgery) 
- Consider for LCIS variants (to rule out concurrent invasive breast cancer).
- The need to achieve R0 resection is unclear as the recurrence rates for close or positive margins are not significant.
Breast cancer risk-reduction options 
- Consider for patients < 65 years of age who opt for a risk-reducing strategy. 
- Agents 
Bilateral prophylactic mastectomy
- Consider in patients with additional risk factors for breast cancer.
Although chemoprevention and bilateral prophylactic mastectomy significantly decrease the risk of breast cancer in patients with LCIS, they are associated with significant adverse effects and the impact of these interventions on overall survival is modest.