CA4 and central nervous system cancer: Downregulation of CA4 is associated with poor prognosis in cancers other than that of the breast, notably uveal melanoma, renal cell cancer, glioma, and lung adenocarcinoma (Liu et al., 2020; Xu et al., 2020), hinting its role in hallmark processes common to many cancers, and its potential significance in establishing such hallmarks in breast cancer progression.