Breast Care A-Z · Condition · LCIS

Lobular carcinoma in situ

also: LCIS, lobular neoplasia, LN, lobular intraepithelial neoplasia · pronounced LOB-yoo-lar

Lobular carcinoma in situ (LCIS) is a non-invasive change in which abnormal cells build up inside the breast lobules; despite its name it is not a true cancer, but it is a marker of higher future risk. You may have been told a biopsy mentions LCIS — the word carcinoma is the most worrying part when first heard, and the explanation can be confusing.

Quick answers

Is LCIS cancer?

Despite the name, classic LCIS is not generally treated as cancer. It is a marker of raised future cancer risk rather than a cancer in its own right. The risk applies to both breasts and the future cancer is often a different type (invasive ductal carcinoma) from the LCIS itself.

Will I need surgery?

For classic LCIS — usually no, surveillance and chemoprevention are the standard pathway. For pleomorphic LCIS — yes, surgical excision is usually recommended. The pathology report distinguishes the two.

Should I have a mastectomy?

LCIS alone is not generally an indication for mastectomy. Risk-reducing mastectomy is considered for patients with LCIS plus additional high-risk factors (BRCA mutation, very strong family history) where the combined risk picture warrants surgery. The decision involves formal risk assessment and a separate consultation.

Lobular Carcinoma In Situ -- Breastory Encyclopaedia Plate LXIII Plate covering LCIS: lobular neoplasia, risk stratification, classic vs pleomorphic, management, and surveillance. ONCOLOGY - PRE-INVASIVE DISEASE PLATE LXIII lobular carcinoma in situ LCIS - lobular neoplasia - LIN (lobular intraepithelial neoplasia) a non-obligate risk marker found incidentally in breast tissue conferring an 8-10-fold increased bilateral breast cancer risk FIG 01 -- TDLU cross-section: Normal lobule (left) | LCIS (right) Normal lobule myoepithelial intact LCIS E-cadherin lost BM intact (no invasion) i -- distended acini filled with lobular cells (LCIS) ii -- discohesive cell population (E-cadherin loss) iii -- basement membrane intact (no invasion) iv -- myoepithelial layer preserved v -- bilateral risk marker (not confined to one site) Classic vs Pleomorphic LCIS Classic LCIS: small uniform cells, low grade Management: surveillance only Pleomorphic LCIS: larger cells, necrosis possible Behaviour: akin to high-grade DCIS Management: consider excision Both: ER+, E-cadherin negative Risk implications LCIS = 8-10x lifetime risk relative to general population Bilateral risk not confined to ipsilateral breast Chemoprevention tamoxifen / anastrozole, not mandatory excision FIG 02 -- LCIS vs DCIS vs Normal: diagnostic comparison Feature LCIS DCIS Cell type Lobular (discohesive) Ductal (cohesive) Architecture Fills acini loosely Fills ducts (cribriform / comedo) E-cadherin Lost Preserved Basement membrane Intact Intact Presentation Incidental finding Calcifications on mammogram Grade Usually low Low - high Invasive counterpart ILC IDC Bilateral risk Yes (both breasts) Ipsilateral focus Management Surveillance + chemoprevention Excision + adjuvant Stage Risk marker (not cancer) Stage 0 (cancer) FIG 03 -- LCIS management options Option Indication Evidence Active surveillance Classic LCIS, low-risk Acceptable -- annual mammogram Tamoxifen Pre-menopausal ~56% risk reduction (NSABP P-1 LCIS subgroup) Anastrozole Post-menopausal IBIS-II: 49% risk reduction Risk-reducing mastectomy Very high-risk + FH Specialist MDT decision Excision biopsy Pleomorphic LCIS / margin NICE recommended MRI screening High-risk per NICE Annual from age 30-40 Genetic testing Family history + LCIS Exclude BRCA Contralateral biopsy Not routine Not standard of care Observation only Patient declines intervention Shared decision FIG 04 -- Clinical pathway: LCIS management 1 Incidental biopsy finding (no mammographic correlate 2 Histological diagnosis (B3 -- lobular 3 Classic vs pleomorphic classification 4 MDT discussion 5 Surveillance plan (mammogram +/- MRI) 6 Chemoprevention discussion + 5-yearly review FIG 05 -- Related procedures and subtypes Classic LCIS (B3) Pleomorphic LCIS (B5 consideration) LCIS with ILC Tamoxifen chemoprevention Anastrozole (post-menopausal) Annual MRI surveillance FIG 06 -- Key statistics 8-10x relative cancer risk vs general population [1] Bilateral risk -- 25-35% lifetime [2] ~56% (NSABP P-1 LCIS subgroup); ~40% overall per NICE NG151 [3] Upgrade to malignancy on excision ~10-15% [4] References 1. Page DL et al. LCIS and cancer risk. Cancer 1991 2. Chuba PJ et al. Bilateral cancer after LCIS. Cancer 2005 3. King TA et al. LCIS management. Ann Surg Oncol 2015 4. NICE NG101. Early breast cancer 2023 5. WHO Classification of Tumours: Breast 5th ed. IARC 2022 Clinically authored by Dr Fiona Tsang-Wright , FRCS (Gen Surg) GMC 4549831 · ORCID 0000-0003-4801-026X
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Definition
Lobular carcinoma in situ — usually shortened to LCIS — is a benign change in the lobules of the breast that is not a cancer in the conventional sense, but is a marker of slightly raised future breast cancer risk in either breast.
1–2% Per-year breast cancer risk after classic LCIS diagnosis 2
30–35% Approximate lifetime risk if diagnosed in the 40s 2
~50% Risk reduction from chemoprevention (tamoxifen / AIs) 4 5

Common questions The questions patients ask first

Is LCIS cancer?
Despite the name, classic LCIS is not generally treated as cancer. It is a marker of raised future cancer risk3 rather than a cancer in its own right. The risk applies to both breasts and the future cancer is often a different type (invasive ductal carcinoma) from the LCIS itself5.
Will I need surgery?
For classic LCIS — usually no, surveillance and chemoprevention are the standard pathway1. For pleomorphic LCIS — yes, surgical excision is usually recommended4. The pathology report distinguishes the two.
Should I have a mastectomy?
LCIS alone is not generally an indication for mastectomy7. Risk-reducing mastectomy is considered for patients with LCIS plus additional high-risk factors (BRCA mutation, very strong family history) where the combined risk picture warrants surgery. The decision involves formal risk assessment and a separate consultation.
What is the difference between LCIS and DCIS?
Both are 'in situ' findings — abnormal cells confined within their normal location. DCIS is a true precursor of invasive ductal cancer and is treated to prevent that progression. LCIS is a risk marker for future cancer in either breast and does not generally require surgical treatment5. Pleomorphic LCIS is the exception — managed more like DCIS4.

Lobular carcinoma in situ — usually shortened to LCIS — is a benign change in the lobules of the breast that is not a cancer in the conventional sense, but is a marker of slightly raised future breast cancer risk in either breast.

LCIS is found incidentally on a biopsy taken for another reason. The name is misleading: the word “carcinoma” makes it sound like cancer, but LCIS does not behave like cancer and is not generally treated as one. It is a risk marker, not a precursor — it indicates raised future risk across both breasts, not a step on the way to invasive cancer in the same place.

Orientation Why you might be reading about this

You may have been told a biopsy result mentions LCIS. The word carcinoma is the most worrying part of the diagnosis when first heard, and the explanation that LCIS is “not really a cancer” can be confusing. This page explains what LCIS is, why the name is misleading, and what it means for surveillance and treatment.

Related terms: DCIS · Invasive lobular carcinoma · Atypical ductal hyperplasia · Core biopsy

Naming Why the name is misleading

The terminology comes from how LCIS appears under the microscope: cells in the lobules look abnormal, fitting the broad definition of “carcinoma in situ” (cancerous-looking cells confined within their normal location). But LCIS does not behave the way DCIS — its ductal counterpart — does:

  • DCIS is a true precursor lesion. Untreated, a meaningful proportion of DCIS would progress to invasive ductal carcinoma over time, and treatment is designed to prevent that.
  • LCIS is a risk marker. It signals that the breast (both breasts, in fact) carries a slightly raised lifetime cancer risk, but the LCIS itself is not what becomes cancer. Surgical removal of an area of LCIS does not eliminate the underlying risk because the risk is across both breasts.

For these reasons, LCIS is increasingly classified by pathologists as lobular neoplasia (a less alarming name)4, with subtypes including:

  • Atypical lobular hyperplasia (ALH) — the milder form4.
  • Classic LCIS — the more extensive form4.
  • Pleomorphic LCIS — a rarer, more aggressive variant that is sometimes treated like DCIS, with surgical excision and clear margins4.

How it’s found How LCIS is found

LCIS is almost always incidental — found on a biopsy taken for some other reason:

  • A biopsy of suspicious microcalcifications turns out to also show LCIS.
  • A biopsy of a fibroadenoma or other benign lesion shows LCIS adjacent to or within the lesion.
  • An MRI-guided biopsy of an enhancing area finds LCIS rather than the expected target.

LCIS does not produce a discrete lump that can be felt, and it does not usually produce specific imaging features. It is a microscopic finding.

Future risk What LCIS means for risk

The lifetime breast cancer risk for a patient with classic LCIS is approximately 1–2% per year3, which translates to a meaningfully raised lifetime risk of around 30–35% if the patient is in her 40s at diagnosis3.

Critically:

  • The risk applies to both breasts, not just the one in which LCIS was found35.
  • The future cancer is more often invasive ductal carcinoma than invasive lobular carcinoma5 — a counter-intuitive finding that confirms LCIS is a marker rather than a direct precursor.
  • The risk is not concentrated in the area where the LCIS was found — surgical excision of the LCIS does not eliminate the elevated risk5.

For pleomorphic LCIS, the picture is different — these cases are managed more like DCIS, with surgical excision aiming for clear margins.

Management Management of classic LCIS

For classic LCIS, the standard pathway is surveillance plus discussion of risk-reducing options:

Surveillance

  • Annual mammography, generally from age 40 in line with NICE CG164 raised-risk surveillance pathways (NHS routine screening from 50)1.
  • Annual breast MRI may be offered where additional NICE CG164 criteria are met (e.g. BRCA/TP53 carrier probability >30%, age 30{nd}49), rather than for LCIS alone1.
  • Clinical examination at intervals1.

Chemoprevention

  • Tamoxifen (5 years, in pre-menopausal patients) reduces the risk of subsequent invasive cancer in LCIS patients by around 50%2.
  • Anastrozole for 5 years is the first-line chemoprevention option for post-menopausal patients under NICE CG164 (tamoxifen is an alternative)16.

Risk-reducing surgery

For patients with LCIS plus additional high-risk factors (BRCA mutation, very strong family history), risk-reducing mastectomy is occasionally considered — but LCIS alone is not generally an indication for surgery7. Most patients are managed with surveillance and chemoprevention.

Exception Pleomorphic LCIS — the exception

Pleomorphic LCIS is a less common subtype with cells that look more atypical and behave more like DCIS4. For pleomorphic LCIS:

  • Surgical excision with clear margins is usually recommended, similar to DCIS47.
  • Adjuvant radiotherapy is sometimes considered7.
  • The case is reviewed at MDT7.

Pathologists distinguish pleomorphic LCIS from classic LCIS on the biopsy report, and the management plan is built around that distinction.

Co-occurrence When LCIS is found alongside another lesion

LCIS is often found incidentally on a biopsy that was looking for something else. The management depends on what else is found:

  • LCIS alone in a biopsy of microcalcifications — usually surveillance, sometimes excision of the calcification area to make sure no DCIS is hiding alongside7.
  • LCIS plus DCIS — managed for the DCIS component, which is the dominant lesion7.
  • LCIS plus atypical ductal hyperplasia (ADH) — usually surgically excised to confirm there is no associated higher-risk change7.
  • LCIS plus invasive cancer — treated for the invasive cancer7.

The MDT reviews the case to confirm the management plan when LCIS is part of a more complex picture7.

At consultation What to discuss at consultation

If your biopsy report mentions LCIS:

  • Which subtype — classic LCIS, ALH, or pleomorphic LCIS — because the management differs.
  • Whether surgical excision is being recommended and why (more often for pleomorphic LCIS, sometimes for classic LCIS in specific contexts).
  • Surveillance plan — frequency and modalities of imaging.
  • Whether chemoprevention is being offered and what the trade-offs are.
  • Family history — whether genetic testing should be considered alongside the LCIS finding.

If you have been offered surgery, or want an independent view of surveillance versus risk-reducing options, a second-opinion consultation is appropriate. Risk-reducing mastectomy is described separately on the risk-reducing mastectomy page.

Resources Further reading

Sources & guidance

Every figure on this page is anchored to a published source. Tap a number in the text or below to jump to the reference.

  1. guideline National Institute for Health and Care Excellence (NICE). Familial breast cancer: classification, care and managing breast cancer and related risks in people with a family history of breast cancer (CG164). London: NICE. 2013 ;Last updated 2023 https://www.nice.org.uk/guidance/cg164 Cited for: UK risk thresholds (population/moderate/high) and surveillance schedules — applies to LCIS-positive patients with high lifetime risk.
  2. rct Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. Journal of the National Cancer Institute. 1998 ;90(18):1371–1388 doi:10.1093/jnci/90.18.1371 Cited for: Tamoxifen reduces invasive breast cancer risk by ~50% in high-risk women including those with LCIS.
  3. cohort Hartmann LC, Degnim AC, Santen RJ, et al. Atypical hyperplasia of the breast — risk assessment and management options. New England Journal of Medicine. 2015 ;372(1):78–89 doi:10.1056/NEJMsr1407164 Cited for: Long-term cumulative risk of breast cancer in atypical hyperplasia / LCIS; bilateral risk distribution; 1–2% per year cumulative risk in classic LCIS.
  4. reference text WHO Classification of Tumours Editorial Board. Breast Tumours. WHO Classification of Tumours, 5th edition, vol. 2. Lyon: International Agency for Research on Cancer. 2019 ;Lobular neoplasia: ALH, classic LCIS, pleomorphic LCIS https://tumourclassification.iarc.who.int/ Cited for: LCIS subtypes — atypical lobular hyperplasia (ALH), classic LCIS, pleomorphic LCIS — and their distinct clinical implications.
  5. cohort King TA, Pilewskie M, Muhsen S, et al. Lobular carcinoma in situ: a 29-year longitudinal experience evaluating clinicopathologic features and breast cancer risk. Journal of Clinical Oncology. 2015 ;33(33):3945–3952 doi:10.1200/JCO.2015.61.4743 Cited for: Long-term LCIS series — bilateral cancer risk, future cancer is more often invasive ductal than lobular, surgical excision does not eliminate risk.
  6. rct Cuzick J, Sestak I, Forbes JF, et al. Anastrozole for prevention of breast cancer in high-risk postmenopausal women (IBIS-II): an international, double-blind, randomised placebo-controlled trial. Lancet. 2014 ;383(9922):1041-1048 doi:10.1016/S0140-6736(13)62292-8 Cited for: IBIS-II: anastrozole reduces breast cancer incidence in high-risk postmenopausal women including those with LCIS or atypical hyperplasia.
  7. guideline National Institute for Health and Care Excellence. Early and locally advanced breast cancer: diagnosis and management (NG101). NICE. 2018 ;Last updated 2024 https://www.nice.org.uk/guidance/ng101 Cited for: UK guideline for surgical and MDT management of in-situ and invasive breast disease; surgical thresholds and risk-reducing pathway.