# Invasive micropapillary carcinoma of the breast

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

## TL;DR

Invasive micropapillary carcinoma is a rare type of breast cancer in which small clusters of cells float inside-out in empty spaces. It spreads to the lymph nodes far more often than ordinary breast cancer of the same size, but once that is allowed for its survival is similar, and it is treated by receptor status like other breast cancer, usually hormone-driven.

## Summary

The WHO classification defines invasive micropapillary carcinoma by morule-like clusters of cells without fibrovascular cores lying in clear stromal spaces, with reversed polarity shown by the inside-out staining of epithelial membrane antigen and sialyl Lewis X (Tan 2020; Archives of Pathology 2016). It is a variant of luminal B breast cancer, hormone-receptor positive with HER2 positivity in a proportion, with frequent lymphovascular invasion and nodal metastasis; molecular studies show distinct profiles supporting its status as an entity but no single genomic aberration explaining its morphology (Archives of Pathology 2016). Laboratory work using MCF7 spheroids modelled the chemoresistance described in the tumour through HIF-1-driven P-glycoprotein expression (BMC Cancer 2012).

How it differs from its parent: its nodal spread is out of proportion to its size, so imaging of the axilla and node surgery matter more; mixed tumours (micropapillary with no special type) are common and the threshold for calling a tumour micropapillary is not agreed.

How common: no reliable share was found in the sources read.

Treatment: by receptor status on the parent's pages, most often as HR-positive breast cancer with endocrine therapy, and with HER2-directed therapy when HER2-positive; there is no trial in the type.

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: Invasive micropapillary carcinoma; IMPC; Micropapillary breast cancer
- Tags: subtype-page; wave4; breast
- Group: breast
- Burden: Rare in its pure form; the criteria separating pure from mixed micropapillary carcinoma remain imprecise, so published shares vary (Archives of Pathology 2016). No population figure is given in the sources read.
- Subtypes: Pure invasive micropapillary carcinoma (luminal B, HR-positive); Mixed micropapillary and no special type carcinoma; HER2-positive micropapillary carcinoma; Mucinous carcinoma with micropapillary pattern (classification debated)
- Biomarkers: Inside-out EMA or MUC1 staining; Oestrogen and progesterone receptor (usually positive), HER2 (positive in a proportion); Lymphovascular invasion and 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/invasive-micropapillary-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/invasive-micropapillary-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/invasive-micropapillary-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/invasive-micropapillary-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/invasive-micropapillary-carcinoma-breast/#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/invasive-micropapillary-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/invasive-micropapillary-carcinoma-breast/#science
- 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/invasive-micropapillary-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/invasive-micropapillary-carcinoma-breast/#living-with-it [7 questions]
- 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/invasive-micropapillary-carcinoma-breast/coming/
- 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/invasive-micropapillary-carcinoma-breast/data/ [1 connected records]

## Standard of care

- All stages: Treated by receptor status on the parent's pages, with careful axillary staging. ([HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [HER2-positive breast cancer](https://onco.cc/cancers/breast-her2-positive/), [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Breast_cancer_classification
- Tan 2020, Histopathology: the 2019 WHO classification of tumours of the breast: https://doi.org/10.1111/his.14091
- Archives of Pathology 2016: invasive micropapillary carcinoma of the breast, an update: https://doi.org/10.5858/arpa.2016-0040-ra
- BMC Cancer 2012: a spheroid model of the chemoresistance of invasive micropapillary carcinoma: https://doi.org/10.1186/1471-2407-12-4

## Connected records

- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [HER2-positive breast cancer](https://onco.cc/cancers/breast-her2-positive/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Invasive breast carcinoma of no special type (invasive ductal carcinoma)](https://onco.cc/cancers/invasive-breast-carcinoma-no-special-type/), [Mucinous carcinoma of the breast](https://onco.cc/cancers/mucinous-carcinoma-breast/), [Papillary carcinomas of the breast (encapsulated, solid and invasive papillary)](https://onco.cc/cancers/papillary-carcinoma-breast/)
- technologies: [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/)

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