# Lobular carcinoma in situ (LCIS)

Source: https://onco.cc/cancers/lobular-carcinoma-in-situ/  
OnCo record `lobular-carcinoma-in-situ` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Lobular carcinoma in situ is not an invasive breast cancer but a marker that a woman is at higher risk of one: abnormal cells fill the milk-producing lobules without spreading. About one in five women develop breast cancer within ten years, in either breast and of any type; preventive tamoxifen cuts that to about one in fourteen, and the pleomorphic form is excised like ductal carcinoma in situ.

## Summary

The WHO classification lists lobular carcinoma in situ among the lobular neoplasias, with atypical lobular hyperplasia as its lesser form and the pleomorphic and florid variants as higher-risk forms; like invasive lobular carcinoma it has lost E-cadherin (Tan 2020). In the Memorial Sloan Kettering cohort of 1,060 women with LCIS alone, 5 percent chose bilateral prophylactic mastectomy and 1,004 chose surveillance, 173 of them with chemoprevention; at a median follow-up of 81 months, 150 women developed 168 breast cancers (63 percent in the same breast, 25 percent in the other, 12 percent both), with no dominant histology (ductal carcinoma in situ 35 percent, invasive ductal 29 percent, invasive lobular 27 percent), and the ten-year cumulative risk was 7 percent with chemoprevention against 21 percent without (King 2015). Pleomorphic LCIS behaves differently: of 21 patients with pure pleomorphic LCIS on biopsy who had excision, 33.3 percent were found to have invasive carcinoma and 19 percent ductal carcinoma in situ, and the lesion was extensive or multifocal in 47.6 percent (Annals of Surgical Oncology 2015).

How it differs from its parent: it is a risk lesion and precursor rather than a cancer, is not staged, and its management is surveillance and prevention rather than treatment of a tumour, which is why it sits beside ductal carcinoma in situ under the breast cancer page.

How common: no incidence figure is given in the sources read.

Treatment: for classic LCIS found on core biopsy, surveillance with annual imaging and consideration of chemoprevention with tamoxifen or an aromatase inhibitor (the low-dose tamoxifen trial TAM-01 included lobular carcinoma in situ among its intraepithelial neoplasias); excision to clear margins for pleomorphic or florid LCIS, given the upgrade rate; bilateral mastectomy only by informed choice (King 2015).

## Fields

- Kind: Cancer
- Last checked: 2026-09-25
- Also known as: LCIS; Lobular neoplasia; Classic lobular carcinoma in situ; Pleomorphic lobular carcinoma in situ; Florid lobular carcinoma in situ; Atypical lobular hyperplasia (lesser form); Tis (LCIS); stage 0 lobular; lobular neoplasia; in situ lobular carcinoma
- Tags: subtype-page; wave4; breast
- Group: breast
- Burden: Found in a minority of breast biopsies, usually by chance; Memorial Sloan Kettering followed 1,060 women with LCIS and no concurrent cancer over 29 years, median age at diagnosis 50 (King 2015). No population incidence is given in the sources read.
- Subtypes: Classic lobular carcinoma in situ (surveillance and chemoprevention); Pleomorphic lobular carcinoma in situ (excised like ductal carcinoma in situ); Florid lobular carcinoma in situ; Atypical lobular hyperplasia (lesser lobular neoplasia)
- Biomarkers: E-cadherin loss; Oestrogen receptor (positive in classic LCIS); Pleomorphic or florid morphology (upgrade risk); Extent on MRI when considering excision

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/lobular-carcinoma-in-situ/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/lobular-carcinoma-in-situ/#overview
- Types and stages (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/lobular-carcinoma-in-situ/#what-it-is [4 subtypes]
- Symptoms and diagnosis (on the hub): How this cancer shows itself, how the diagnosis is confirmed, and the biomarkers clinicians test for. https://onco.cc/cancers/lobular-carcinoma-in-situ/#finding-it [4 biomarkers]
- Treatment (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/lobular-carcinoma-in-situ/#treating-it [2 settings]
- Trials and papers (on the hub): Trials recruiting now, the landmark trials, the trials held by this cancer's subtypes, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/lobular-carcinoma-in-situ/#evidence [1 trial]
- Biology and targets (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/lobular-carcinoma-in-situ/#science [2 targets]
- Countries and centres (own page): Cases by country, the UK and NHS pathway and other country lenses, the expert centres with trials on record, and the centres named on this cancer's subtypes. https://onco.cc/cancers/lobular-carcinoma-in-situ/where-you-are/ [16 UK centres]
- Decisions and support (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/lobular-carcinoma-in-situ/#living-with-it [10 questions, 4 red cards]
- Pipeline and open problems (own page): Everything in development, the medicines held by this cancer's subtypes, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/lobular-carcinoma-in-situ/coming/ [1 medicine]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/lobular-carcinoma-in-situ/data/ [13 connected records, 1 note]

## Standard of care

- Classic LCIS on biopsy: Surveillance and chemoprevention (tamoxifen or an aromatase inhibitor); TAM-01 tested low-dose tamoxifen in intraepithelial neoplasia. ([Tamoxifen](https://onco.cc/drugs/tamoxifen/), [TAM-01](https://onco.cc/trials/tam-01/), [Aromatase inhibitor](https://onco.cc/terms/aromatase-inhibitor/))
- Pleomorphic or florid LCIS: Excision to clear margins because of the upgrade rate to invasive cancer or ductal carcinoma in situ. ([Ductal carcinoma in situ (DCIS)](https://onco.cc/cancers/ductal-carcinoma-in-situ/), [Mastectomy](https://onco.cc/terms/mastectomy/))

## Notes

- Why lobular carcinoma in situ is on its own page rather than under a receptor subtype. It is staged Tis (LCIS) and, unlike ductal carcinoma in situ, classical lobular carcinoma in situ behaves more as a marker of risk in both breasts than as a lesion that will become an invasive cancer where it sits. The 2024 UK dataset expanded its description to cover the florid and pleomorphic forms, which are treated more like ductal carcinoma in situ.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Lobular_carcinoma_in_situ
- Tan 2020, Histopathology: the 2019 WHO classification of tumours of the breast: https://doi.org/10.1111/his.14091
- King 2015, JCO: lobular carcinoma in situ, a 29-year longitudinal experience of 1,060 patients: https://doi.org/10.1200/jco.2015.61.4743
- Annals of Surgical Oncology 2015: pleomorphic lobular carcinoma in situ, features and management: https://doi.org/10.1245/s10434-015-4552-x
- Cancer Research UK: types of breast cancer: https://www.cancerresearchuk.org/about-cancer/breast-cancer/types
- Royal College of Pathologists G148: dataset for histopathological reporting of breast disease in surgical excision specimens of breast cancer, version 3, November 2024 (full review due November 2026): https://www.rcpath.org/resourceLibrary/g148-dataset-for-histopathological-reporting-of-breast-disease-in-surgical-excision-specimens-of-breast-cancer.html

## Connected records

- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Ductal carcinoma in situ (DCIS)](https://onco.cc/cancers/ductal-carcinoma-in-situ/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Invasive lobular carcinoma of the breast](https://onco.cc/cancers/invasive-lobular-carcinoma/)
- targets: [CDH1](https://onco.cc/targets/cdh1/)
- drugs: [Tamoxifen](https://onco.cc/drugs/tamoxifen/)
- terms: [Aromatase inhibitor](https://onco.cc/terms/aromatase-inhibitor/), [Carcinoma in situ (CIS)](https://onco.cc/terms/carcinoma-in-situ/), [Ducts, lobules and the terminal duct lobular unit](https://onco.cc/terms/terminal-duct-lobular-unit/), [Mastectomy](https://onco.cc/terms/mastectomy/), [The WHO classification of breast tumours, and what the 6th edition changed](https://onco.cc/terms/who-breast-classification/), [Which staging edition a breast report uses: UICC TNM 8, TNM 9 and the AJCC prognostic stage](https://onco.cc/terms/tnm-breast-cancer-editions/)
- trials: [TAM-01](https://onco.cc/trials/tam-01/)

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JSON: https://onco.cc/api/v1/entities/lobular-carcinoma-in-situ.json