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.
- The annual incidence of breast cancer in patients with LCIS is ∼ 2% per year. 
- Invasive breast cancer can occur in the ipsilateral or contralateral breast in patients with LCIS.
- LCIS has a lower risk of subsequent invasive carcinoma compared to DCIS.
LCIS was previously classified as a premalignant lesion (i.e., Tis). It is now considered a benign entity and has been removed from the 8th edition of the AJCC TNM cancer staging system. 
Epidemiological data refers to the US, unless otherwise specified.
|Histological classification of LCIS |
|Classic LCIS (CLCIS)|| |
|LCIS variants ||Pleomorphic LCIS (PLCIS)|| |
|Florid LCIS (FLCIS)|| |
- Asymptomatic; no specific findings (no mass or calcifications)
- Approx. 55% are multicentric and approx. 35% are bilateral 
Classic LCIS is typically not apparent on clinical breast examination or imaging. In PLCIS, pleomorphic calcifications may be seen on mammography. 
- LCIS is usually detected incidentally during biopsy for another abnormality. 
Immunohistochemistry ; 
- E-cadherin: negative
- p120 catenin: diffuse cytoplasmic staining
- Receptor testing: may show estrogen and progesterone positive, HER2 negative 
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 
- Annual mammogram with or without digital breast tomosynthesis
- Alternatively, breast MRI may be considered in patients with additional risk factors for breast cancer (e.g., family history of breast cancer).
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.
Surgical excision to rule out associated invasive breast cancer is not routinely recommended for classic LCIS. 
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.