# Mucinous carcinoma of the breast

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

## TL;DR

Mucinous carcinoma is a rare type of breast cancer in which the cancer cells float in pools of mucus they have made. It is usually hormone-receptor positive, slow-growing and less likely to reach the lymph nodes than ordinary breast cancer, so its outlook is good and it is treated like other hormone-driven breast cancer.

## Summary

The WHO classification defines pure mucinous carcinoma by clusters of low-grade cells in lakes of extracellular mucin making up over 90 percent of the tumour, and separates it from mixed mucinous carcinoma and from mucinous cystadenocarcinoma (Tan 2020). In a Taiwanese series of 93 pure mucinous carcinomas compared with 2,674 infiltrating ductal carcinomas, hormone receptor expression was higher and grade, hormone receptor status and node involvement were all more favourable, confirming its less aggressive behaviour (World J Surg Oncol 2013).

How it differs from its parent: mucin makes the tumour soft and well-circumscribed, so it can look benign on imaging; nodal spread is uncommon in the pure form; and the mixed form (mucinous with ordinary no special type carcinoma) behaves like the ordinary component and is treated as such.

How common: about 3.5 percent of breast cancers in the Taiwanese series (World J Surg Oncol 2013).

Treatment: as HR-positive breast cancer, following the parent page, with endocrine therapy and usually no chemotherapy for the pure form; the sources read report treatment patterns, not trials in this type.

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: Mucinous carcinoma of the breast; Colloid carcinoma of the breast; Mucinous breast cancer; Pure mucinous carcinoma
- Tags: subtype-page; wave4; breast
- Group: breast
- Burden: About 3.5 percent of newly diagnosed breast cancers in Taiwan (World J Surg Oncol 2013); typically a cancer of older women. No UK figure was found in the sources read.
- Subtypes: Pure mucinous carcinoma (over 90 percent mucinous; luminal A); Mixed mucinous carcinoma (treated as its no special type component); Mucinous carcinoma with neuroendocrine differentiation (hypercellular type B); Mucinous cystadenocarcinoma (very rare)
- Biomarkers: Proportion of mucinous component (over 90 percent for pure); Oestrogen and progesterone receptor (usually positive), HER2 (usually negative); Node status

## 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/mucinous-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/mucinous-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/mucinous-carcinoma-breast/#what-it-is [4 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/mucinous-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/mucinous-carcinoma-breast/#treating-it [1 setting, 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/mucinous-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/mucinous-carcinoma-breast/#science [1 target]
- 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/mucinous-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/mucinous-carcinoma-breast/#living-with-it [8 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/mucinous-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/mucinous-carcinoma-breast/data/ [7 connected records]

## Standard of care

- All stages: Treated as HR-positive breast cancer: surgery, radiotherapy after breast conservation, endocrine therapy; chemotherapy for the mixed form as for no special type disease. ([HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/), [Tamoxifen](https://onco.cc/drugs/tamoxifen/), [Letrozole (and other aromatase inhibitors)](https://onco.cc/drugs/letrozole/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Mucinous_carcinoma
- Tan 2020, Histopathology: the 2019 WHO classification of tumours of the breast: https://doi.org/10.1111/his.14091
- World J Surg Oncol 2013: pure mucinous carcinoma of the breast, 93 cases against 2,674 ductal carcinomas: https://doi.org/10.1186/1477-7819-11-139
- Cancer Research UK: types of breast cancer: https://www.cancerresearchuk.org/about-cancer/breast-cancer/types

## Connected records

- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Invasive micropapillary carcinoma of the breast](https://onco.cc/cancers/invasive-micropapillary-carcinoma-breast/), [Neuroendocrine neoplasms of the breast](https://onco.cc/cancers/neuroendocrine-neoplasms-breast/), [Papillary carcinomas of the breast (encapsulated, solid and invasive papillary)](https://onco.cc/cancers/papillary-carcinoma-breast/), [Tubular carcinoma of the breast](https://onco.cc/cancers/tubular-carcinoma-breast/)
- technologies: [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/)
- drugs: [Letrozole (and other aromatase inhibitors)](https://onco.cc/drugs/letrozole/), [Tamoxifen](https://onco.cc/drugs/tamoxifen/)

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