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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.
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).
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.
Most cancers start in the ducts and drain first to the axillary nodes, which is why the armpit is checked and a sentinel node is sampled.
Same organ: Triple-negative breast cancer (TNBC), Breast cancer (all types), HR-positive / HER2-negative breast cancer, HER2-positive breast cancer, Male breast cancer, Ductal carcinoma in situ (DCIS), High-risk early HR-positive breast cancer, HR-positive metastatic breast cancer after CDK4/6 inhibitors, HER2-low and HER2-ultralow metastatic breast cancer, Early HER2-positive breast cancer, HER2-positive breast cancer with brain metastases, Early triple-negative breast cancer, Metastatic triple-negative breast cancer, Basal-like 1 triple-negative breast cancer (BL1), Basal-like 2 triple-negative breast cancer (BL2), Mesenchymal triple-negative breast cancer (M), Mesenchymal stem-like triple-negative breast cancer (MSL), Luminal androgen receptor triple-negative breast cancer (LAR), Immunomodulatory triple-negative breast cancer (IM), Metaplastic breast carcinoma, Carcinoma with medullary pattern (medullary breast cancer), Adenoid cystic carcinoma of the breast, Apocrine carcinoma of the breast, Secretory carcinoma of the breast, BRCA-associated triple-negative breast cancer, Inflammatory breast cancer, Paget disease of the nipple, Phyllodes tumour of the breast, Invasive lobular carcinoma of the breast, Invasive breast carcinoma of no special type (invasive ductal carcinoma), Tubular carcinoma of the breast, Mucinous carcinoma of the breast, Papillary carcinomas of the breast (encapsulated, solid and invasive papillary), Invasive cribriform carcinoma of the breast, Invasive breast carcinoma with medullary pattern (medullary carcinoma), Invasive micropapillary carcinoma of the breast, Neuroendocrine neoplasms of the breast
Surveillance and chemoprevention (tamoxifen or an aromatase inhibitor); TAM-01 tested low-dose tamoxifen in intraepithelial neoplasia.
Excision to clear margins because of the upgrade rate to invasive cancer or ductal carcinoma in situ.
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Query for this cancer: (TITLE:"Lobular carcinoma in situ" OR ABSTRACT:"Lobular carcinoma in situ" OR TITLE:"LCIS" OR ABSTRACT:"LCIS" OR TITLE:"Lobular neoplasia" OR ABSTRACT:"Lobular neoplasia" OR TITLE:"Classic lobular carcinoma in situ" OR ABSTRACT:"Classic lobular carcinoma in situ" OR TITLE:"Pleomorphic lobular carcinoma in situ" OR ABSTRACT:"Pleomorphic lobular carcinoma in situ" OR TITLE:"Florid lobular carcinoma in situ" OR ABSTRACT:"Florid lobular carcinoma in situ") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Lobular carcinoma in situ (LCIS), not a curated reading list.
The targets of this cancer's medicines and the ones linked to it directly.
Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record.
One section per setting: the options named, what each is for, the trials behind them, the recorded trade-offs and the questions to ask.
A swollen painful calf, or sudden breathlessness with chest pain; the tamoxifen boxed warning covers pulmonary embolism and stroke.
Possible QT prolongation. Check ECG and electrolytes; review other QT-prolonging drugs.
Blood clots in the leg veins or lungs. Cancer makes blood clot more easily and some treatments (IMiDs, anti-VEGF drugs, hormone therapy, central lines, surgery) add risk; clots are the second commonest cause of death in cancer patients after the cancer itself.
See all on the product pages:Tamoxifen·Printable cards in the navigator
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