# Claudin-low breast cancer

Source: https://onco.cc/terms/claudin-low/  
OnCo record `claudin-low` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Claudin-low breast cancers have lost the claudin proteins that hold epithelial cells together and have taken on the features of migrating, stem-like cells. Most are triple-negative and respond to chemotherapy less well than basal-like cancers. Newer work treats claudin-low as a pattern that can overlay any subtype rather than a subtype of its own.

## Summary

Prat and colleagues characterised the claudin-low subtype across an updated human tumour database, cell lines and mouse models: low to absent expression of luminal differentiation markers, high enrichment for epithelial-to-mesenchymal transition markers, immune response genes and cancer stem cell-like features; clinically most are poor-prognosis ER-, PR- and HER2-negative invasive ductal carcinomas with a high frequency of metaplastic and medullary differentiation, with a response rate to standard preoperative chemotherapy intermediate between basal-like and luminal tumours; the subtype most closely resembles the mammary epithelial stem cell in a differentiation hierarchy (Prat 2010). Fougner and colleagues re-examined claudin-low tumours with genomic, transcriptomic and clinical data and concluded that claudin-low is not a subtype analogous to the intrinsic subtypes but a complex additional phenotype that may permeate tumours of various intrinsic subtypes, distinguished by low genomic instability, low mutational burden, low proliferation and high immune and stromal infiltration while otherwise reflecting the intrinsic subtype; they also found weaknesses in the established classifier (Fougner 2020). In Lehmann's triple-negative classification the mesenchymal and mesenchymal stem-like subtypes carry the same epithelial-to-mesenchymal transition biology, and the parent record names mesenchymal and claudin-low disease as the biology that resists chemotherapy, ADC payloads and immunotherapy alike.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: Claudin-low subtype; Claudin-low phenotype; Claudin-low triple-negative breast cancer
- Tags: breast; tnbc

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Claudin
- Prat, Breast Cancer Res 2010: phenotypic and molecular characterisation of the claudin-low intrinsic subtype: https://doi.org/10.1186/bcr2635
- Fougner, Nat Commun 2020: re-definition of claudin-low as a breast cancer phenotype: https://doi.org/10.1038/s41467-020-15574-5
- Lehmann, J Clin Invest 2011: identification of human triple-negative breast cancer subtypes (BL1, BL2, IM, M, MSL, LAR): https://doi.org/10.1172/jci45014

## Connected records

- cancers: [Mesenchymal stem-like triple-negative breast cancer (MSL)](https://onco.cc/cancers/tnbc-mesenchymal-stem-like/), [Mesenchymal triple-negative breast cancer (M)](https://onco.cc/cancers/tnbc-mesenchymal/), [Metaplastic breast carcinoma](https://onco.cc/cancers/metaplastic-breast-carcinoma/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- pathways: [Epithelial-mesenchymal transition & drug efflux](https://onco.cc/pathways/emt/)
- terms: [Basal-like breast cancer](https://onco.cc/terms/basal-like/)

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JSON: https://onco.cc/api/v1/entities/claudin-low.json