# Mesenchymal stem-like triple-negative breast cancer (MSL)

Source: https://onco.cc/cancers/tnbc-mesenchymal-stem-like/  
OnCo record `tnbc-mesenchymal-stem-like` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Mesenchymal stem-like was one of the six original subtypes of triple-negative breast cancer, marked by stem-cell and low-proliferation genes. Five years later the same group showed the signal came from stromal cells mixed into the sample rather than the cancer cells, so the label describes a tumour environment rather than a tumour.

## Summary

Lehmann 2011 separated a mesenchymal stem-like (MSL) cluster from the mesenchymal cluster by lower expression of proliferation genes and enrichment for genes of mesenchymal stem cells, angiogenesis and growth factor signalling; representative cell lines responded to the PI3K/mTOR inhibitor NVP-BEZ235 and to dasatinib (Lehmann 2011). Using histopathological quantification and laser-capture microdissection, the 2016 refinement showed that the MSL transcripts were contributed by tumour-associated stromal cells, as the immunomodulatory transcripts were by infiltrating lymphocytes, and collapsed the classification to four tumour-specific subtypes (Lehmann 2016). The page stays because the label persists in papers and reports; a tumour once called MSL would now be assigned to the mesenchymal or another intrinsic subtype, and its low proliferation and stromal richness match the claudin-low phenotype described by Fougner 2020.

A research classification by gene expression (Lehmann 2011, refined 2016), not a test the NHS runs; treatment follows the triple-negative rows on the parent page.

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: MSL subtype; Mesenchymal stem-like TNBC
- Tags: breast; tnbc; subtype-page
- Group: breast
- Burden: One of the six 2011 Lehmann subtypes; dropped as a tumour-intrinsic subtype in 2016 when its signal was traced to stromal cells.
- Subtypes: Mesenchymal tumours with a stromal, low-proliferation signature (claudin-low phenotype)
- Biomarkers: Stromal and mesenchymal stem-cell gene expression (a sample-composition signal, research only)

## 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/tnbc-mesenchymal-stem-like/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/tnbc-mesenchymal-stem-like/#overview
- What it is (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/tnbc-mesenchymal-stem-like/#what-it-is [1 subtype]
- Finding it (on the hub): How it shows itself, how it is confirmed, what screening exists, and the biomarkers clinicians test for. https://onco.cc/cancers/tnbc-mesenchymal-stem-like/#finding-it [1 biomarker]
- Treating it (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/tnbc-mesenchymal-stem-like/#treating-it [1 setting]
- Evidence (on the hub): Trials recruiting now, the landmark trials, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/tnbc-mesenchymal-stem-like/#evidence [1 trial]
- The science (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/tnbc-mesenchymal-stem-like/#science [1 target, 1 pathway]
- Where you are (own page): Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record. https://onco.cc/cancers/tnbc-mesenchymal-stem-like/where-you-are/
- Living with it (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/tnbc-mesenchymal-stem-like/#living-with-it [9 questions, 3 red cards]
- What is coming (own page): Everything in development, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/tnbc-mesenchymal-stem-like/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/tnbc-mesenchymal-stem-like/data/ [7 connected records]

## Standard of care

- Any stage: As for triple-negative disease; the label has no treatment consequence. ([Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [KEYNOTE-522](https://onco.cc/trials/keynote-522/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Triple-negative_breast_cancer
- 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
- Lehmann, PLoS One 2016: refinement of triple-negative breast cancer molecular subtypes to four (TNBCtype-4): https://doi.org/10.1371/journal.pone.0157368
- Fougner, Nat Commun 2020: re-definition of claudin-low as a breast cancer phenotype: https://doi.org/10.1038/s41467-020-15574-5

## Connected records

- cancers: [Immunomodulatory triple-negative breast cancer (IM)](https://onco.cc/cancers/tnbc-immunomodulatory/), [Mesenchymal triple-negative breast cancer (M)](https://onco.cc/cancers/tnbc-mesenchymal/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- pathways: [Epithelial-mesenchymal transition & drug efflux](https://onco.cc/pathways/emt/)
- terms: [Claudin-low breast cancer](https://onco.cc/terms/claudin-low/)
- drugs: [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/)
- trials: [KEYNOTE-522](https://onco.cc/trials/keynote-522/)

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JSON: https://onco.cc/api/v1/entities/tnbc-mesenchymal-stem-like.json