Is lobular carcinoma in situ (LCIS) considered cancer?

Lobular Carcinoma In Situ (LCIS) Is Not Cancer But a Risk Marker

Lobular carcinoma in situ (LCIS) is not considered cancer but rather a marker of increased risk for developing breast cancer in the future. 1 LCIS represents a distinct pathologic entity that identifies women who have a higher likelihood of developing invasive breast cancer, but it is not itself a malignant or premalignant lesion requiring treatment as cancer.

Understanding LCIS

LCIS is classified as a "pure noninvasive carcinoma" in breast cancer staging (stage 0) 1, but its clinical significance differs substantially from ductal carcinoma in situ (DCIS), which is considered a true precursor to invasive cancer.

Key characteristics of LCIS include:

• Risk indicator rather than precursor: LCIS serves primarily as a marker identifying women at increased risk for future breast cancer development 1, 2
• Bilateral risk: The risk for developing invasive breast cancer after LCIS diagnosis is equal in both breasts, regardless of which breast contained the original LCIS 1
• Long-term risk: Most subsequent invasive cancers occur more than 15 years after the initial LCIS diagnosis 1, 2
• Risk magnitude: Lifetime risk of developing invasive breast cancer ranges from 10% to 20% 1, which equates to approximately 0.5% to 1.0% annual risk 1, 3
• Cancer type: Subsequent invasive cancers are often ductal rather than lobular in nature 2, 4

Management Approach for LCIS

Since LCIS is not cancer but a risk marker, management focuses on surveillance and risk reduction:

1. Observation (preferred approach):

   • Interval history and physical examinations every 6-12 months 1
   • Annual diagnostic mammography 1
   • This approach is recommended because the risk of developing invasive carcinoma is relatively low (approximately 21% over 15 years) 1

2. Chemoprevention options:

   • Tamoxifen for premenopausal women 1
   • Tamoxifen or raloxifene for postmenopausal women 1
   • These medications can reduce the risk of developing invasive breast cancer by approximately 46% 1, 3

3. Surgical options (generally not recommended for most patients):

   • Bilateral risk-reduction mastectomy should only be considered in special circumstances, such as:
     • Women with BRCA1/2 mutations
     • Women with strong family history of breast cancer 1
   • If mastectomy is considered, it must be bilateral since the risk applies to both breasts 1

Important Considerations and Caveats

• Pathologic review: LCIS can be difficult to distinguish from atypical hyperplasia or early invasive carcinoma, so thorough pathologic review is essential 1
• No need for clear margins: Unlike DCIS, there is no need to excise biopsy sites of LCIS to obtain clear margins 2
• Pleomorphic LCIS: Some histologically aggressive variants of LCIS (e.g., pleomorphic LCIS) may have greater potential to develop into invasive lobular carcinoma, but outcome data for these variants are lacking 1
• Increasing incidence: The rate of LCIS diagnosis has increased in recent years, likely due to more rigorous breast cancer screening 5, 6
• Trend toward overtreatment: Despite current recommendations, there has been a concerning 50% increase in mastectomy rates for LCIS between 2000-2009 5

Clinical Decision Algorithm

1. Confirm diagnosis: Ensure pathologic review confirms pure LCIS without invasive components
2. Risk assessment: Consider additional risk factors (family history, genetic mutations)
3. Standard approach: Recommend observation with regular surveillance for most patients
4. Consider chemoprevention: Discuss tamoxifen or raloxifene as risk-reduction options
5. Surgical consideration: Reserve bilateral mastectomy discussion only for high-risk patients (BRCA carriers, strong family history)

LCIS should be approached as a risk factor requiring careful monitoring rather than as a cancer requiring aggressive treatment. The excellent prognosis for women with LCIS underscores the importance of avoiding overtreatment while maintaining appropriate surveillance.