PIK3CA and overgrowth syndrome: Rather than only including actionable variants for mosaic disease, we show with our case report a clinical proof-of-concept that LB can be extended from cancers to all heterogeneous diseases such as mosaic diseases, including asymmetric overgrowth syndromes (e.g. Proteus syndrome, Klippel-Trennaunay syndrome and PIK3CA-related overgrowth spectrum, PROS, as well as many others).