Although evidence suggests that MAMDC2 plays a tumor-suppressing role in ER+ breast cancer, our study found that MAMDC2 is significantly upregulated in CMS4 CRC and correlates with aggressive tumor features, such as high TSR and peritoneal metastasis, and promotes the EMT of CRC cells, suggesting it may have a tumor-promoting effect. The gene discussed is MAMDC2; the disease is breast carcinoma.