MUC16 and cancer: One potential mechanism for differences in CA-125 thresholds is that CA-125 is an epitope of MUC-16, a much larger glycoprotein expressed on neutrophils.32 Thus, CA-125 level is correlated with neutrophil count in women with cancer33 across histology types34,35 and in women without cancer.15 At the cellular level, the expression levels of MUC-16 in fallopian tubes with benign tumors are similar between women who identify as Black and as White (Ronny Drapkin, MD, University of Pennsylvania Perelman School of Medicine, email, April 1, 2024).