{"entity":{"id":"invasive-micropapillary-carcinoma-breast","kind":"cancer","name":"Invasive micropapillary carcinoma of the breast","aka":["Invasive micropapillary carcinoma","IMPC","Micropapillary breast cancer"],"tldr":"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).\n\nHow 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.\n\nHow common: no reliable share was found in the sources read.\n\nTreatment: 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.","asOf":"2026-09-24","wikipedia":"https://en.wikipedia.org/wiki/Breast_cancer_classification","links":[{"label":"Tan 2020, Histopathology: the 2019 WHO classification of tumours of the breast","url":"https://doi.org/10.1111/his.14091"},{"label":"Archives of Pathology 2016: invasive micropapillary carcinoma of the breast, an update","url":"https://doi.org/10.5858/arpa.2016-0040-ra"},{"label":"BMC Cancer 2012: a spheroid model of the chemoresistance of invasive micropapillary carcinoma","url":"https://doi.org/10.1186/1471-2407-12-4"}],"tags":["subtype-page","wave4","breast"],"related":["breast-cancer","breast-hr-positive","papillary-carcinoma-breast","mucinous-carcinoma-breast","invasive-breast-carcinoma-no-special-type"],"cancers":[],"sections":[],"technologies":["endocrine-therapy"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"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"],"standardOfCare":[{"setting":"All stages","approach":"Treated by receptor status on the parent's pages, with careful axillary staging.","refs":["breast-hr-positive","breast-her2-positive","endocrine-therapy"]}],"stateOfArt":[],"history":[],"pipeline":[],"openProblems":[],"parent":"breast-cancer"},"route":"/cancers/invasive-micropapillary-carcinoma-breast/","neighbours":{"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"breast-her2-positive","kind":"cancer","name":"HER2-positive breast cancer","route":"/cancers/breast-her2-positive/"},{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"invasive-breast-carcinoma-no-special-type","kind":"cancer","name":"Invasive breast carcinoma of no special type (invasive ductal carcinoma)","route":"/cancers/invasive-breast-carcinoma-no-special-type/"},{"id":"mucinous-carcinoma-breast","kind":"cancer","name":"Mucinous carcinoma of the breast","route":"/cancers/mucinous-carcinoma-breast/"},{"id":"papillary-carcinoma-breast","kind":"cancer","name":"Papillary carcinomas of the breast (encapsulated, solid and invasive papillary)","route":"/cancers/papillary-carcinoma-breast/"}],"technology":[{"id":"endocrine-therapy","kind":"technology","name":"Endocrine therapy (SERMs, AIs, SERDs)","route":"/technologies/endocrine-therapy/"}]}}