Regarding the clinical impact on the course of cancer, KLK9 has been reported to be a prognostic marker in different tumor entities: in glioma patients, stronger KLK9 immunostaining is associated with an unfavorable prognosis [6], whereas in breast cancer, KLK9-positive patients (on mRNA levels) had longer disease-free and overall survival [39]. This evidence concerns the gene KLK9 and breast cancer.