# Secretory carcinoma of the breast

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

## TL;DR

Secretory carcinoma is a very rare, slow-growing breast cancer first described in children, whose cells make milk-like secretions. It is usually triple-negative but almost always carries the ETV6-NTRK3 gene fusion, so the rare patient whose tumour spreads can be treated with an NTRK inhibitor tablet, and most need no chemotherapy.

## Summary

Secretory breast carcinoma is a rare subtype of infiltrating ductal-origin carcinoma that expresses the ETV6-NTRK3 gene fusion, first cloned in paediatric mesenchymal cancers; the fusion was confirmed in 12 of 13 cases (92 percent) but in no other ductal carcinomas, and its expression transformed mammary epithelial cells into gland-forming tumours in mice, establishing it as a primary oncogenic event (Tognon 2002). Histologically the tumour shows microcystic, solid and tubular patterns with abundant intracellular and extracellular secretion, is usually low grade and often triple-negative or weakly ER-positive with a basal-like immunophenotype (Cserni 2021; Thomas 2023). The European Working Group for Breast Screening Pathology places secretory carcinoma among the triple-negative special types with an indolent course whose patients are unlikely to benefit from systemic chemotherapy, favouring surgery with or without radiotherapy (Cserni 2021). Because the ETV6-NTRK3 fusion is an NTRK fusion, the tumour-agnostic approvals of larotrectinib and entrectinib apply to the rare metastatic case.

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: Juvenile carcinoma of the breast; Secretory breast carcinoma; SBC; ETV6-NTRK3 fusion-positive breast carcinoma
- Tags: breast; tnbc; subtype-page
- Group: breast
- Burden: Very rare (under 0.15 percent of breast cancers in most series; the review literature counts it among the 5 to 10 percent of triple-negative cancers that are rare subtypes); it can occur in children and young adults as well as adults (Thomas 2023).
- Subtypes: Secretory carcinoma arising in children and adolescents (juvenile carcinoma); Adult secretory carcinoma (the majority of cases); Invasive carcinoma of no special type (ductal) with secretory features
- Biomarkers: ETV6-NTRK3 fusion (about 92 percent) and pan-TRK immunohistochemistry; Triple-negative or low ER status with low grade; S100 and mammaglobin expression

## 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/secretory-carcinoma-breast/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/secretory-carcinoma-breast/#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/secretory-carcinoma-breast/#what-it-is [3 subtypes]
- 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/secretory-carcinoma-breast/#finding-it [3 biomarkers]
- 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/secretory-carcinoma-breast/#treating-it [2 settings, 1 decision with options]
- 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/secretory-carcinoma-breast/#evidence
- 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/secretory-carcinoma-breast/#science [3 targets]
- 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/secretory-carcinoma-breast/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/secretory-carcinoma-breast/#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/secretory-carcinoma-breast/coming/ [2 medicines]
- 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/secretory-carcinoma-breast/data/ [14 connected records]

## Standard of care

- Localised disease: Surgery with clear margins, radiotherapy after breast conservation; chemotherapy is usually not indicated for this indolent type (European working group consensus). ([Lumpectomy (breast-conserving surgery)](https://onco.cc/terms/lumpectomy/), [Mastectomy](https://onco.cc/terms/mastectomy/), [Sentinel lymph node biopsy](https://onco.cc/technologies/sentinel-node/))
- Metastatic disease (rare): NTRK inhibitors (larotrectinib, entrectinib) under their tumour-agnostic approvals for NTRK fusion-positive solid tumours. ([Larotrectinib](https://onco.cc/drugs/larotrectinib/), [Entrectinib](https://onco.cc/drugs/entrectinib/), [Tumour-agnostic (tissue-agnostic) approval](https://onco.cc/terms/tumour-agnostic/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Secretory_carcinoma
- Tognon, Cancer Cell 2002: the ETV6-NTRK3 gene fusion as a primary event in secretory breast carcinoma: https://doi.org/10.1016/s1535-6108(02)00180-0
- Cserni, Cancers 2021: triple-negative breast cancer histological subtypes with a favourable prognosis (European Working Group for Breast Screening Pathology): https://doi.org/10.3390/cancers13225694
- Thomas, NPJ Breast Cancer 2023: rare subtypes of triple-negative breast cancer: https://doi.org/10.1038/s41523-023-00554-x

## Connected records

- cancers: [Acinic cell carcinoma of the salivary glands](https://onco.cc/cancers/acinic-cell-carcinoma-salivary/), [Adenoid cystic carcinoma of the breast](https://onco.cc/cancers/adenoid-cystic-carcinoma-breast/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- drugs: [Entrectinib](https://onco.cc/drugs/entrectinib/), [Larotrectinib](https://onco.cc/drugs/larotrectinib/)
- terms: [Grade](https://onco.cc/terms/tumour-grade/), [Lumpectomy (breast-conserving surgery)](https://onco.cc/terms/lumpectomy/), [Mastectomy](https://onco.cc/terms/mastectomy/), [Tumour-agnostic (tissue-agnostic) approval](https://onco.cc/terms/tumour-agnostic/)
- technologies: [Sentinel lymph node biopsy](https://onco.cc/technologies/sentinel-node/)

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JSON: https://onco.cc/api/v1/entities/secretory-carcinoma-breast.json