Mucinous cystadenocarcinoma of the breast harbours TRPS1 expressions and PIK3CA alterations.

To our knowledge, this is the first demonstration of TRPS1 expression in BMCA patients and the first identification of a PIK3CA hotspot mutation in these tumours. These findings provide insights into the molecular mechanisms underlying BMCA tumorigenesis and suggest a potential drug target for this rare and poorly understood cancer.