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4 slides generated from the cancer page, with a quiz from the open benchmark and speaker notes that cite the sources. Arrow keys move between slides; Print gives one slide per page.
Micropapillary adenocarcinoma is bowel cancer in which some of the tumour grows as tiny clusters of cells floating in empty spaces, with the cells turned inside out so the surface that normally faces the bowel faces outwards instead. It is a pattern that goes with heavier invasion of lymph and blood vessels and more involved lymph nodes, and it is graded and treated like ordinary bowel cancer.
What it is. The 2019 World Health Organization classification of digestive tumours lists micropapillary adenocarcinoma among the histological subtypes of colorectal adenocarcinoma (Nagtegaal 2020). Under the microscope the tumour forms small morula-like nests of cells without a fibrovascular core, sitting in empty lacunar spaces, and the cells show reversed polarity: the apical membrane faces the stroma rather than a lumen, which can be shown by staining for villin or epithelial membrane antigen (Oncol Lett 2021).
How it differs from its parent. The micropapillary component is almost never the whole tumour. Reported proportions range from 5 to 80 percent of a lesion and are usually under 30 percent (J Gastrointest Cancer 2026). Where it is present, tumours show more lymphatic and vascular invasion, a higher ratio of involved to examined lymph nodes and a higher pathological T category than colorectal cancers without it, and more invasion again as the proportion rises (Hum Pathol 2018). KRAS, BRAF and TP53 mutations are described in the pattern and are read as driving invasiveness and the loss of polarity rather than defining a separate disease (J Gastrointest Cancer 2026).
| Setting | Approach | Guideline |
|---|---|---|
| Localised disease | Resection with the usual nodal harvest; adjuvant chemotherapy decided by stage as for colorectal adenocarcinoma of no special type, with the node involvement that travels with this pattern taken into account. | not mapped |