By analyzing the expression of secreted SCUBE2 protein in the serum of patients from the Qilu cohort, Wu et al. observed an upregulation of SCUBE2 expression in bone metastasis patients (n = 13) compared to patients without distant recurrence (n = 23), confirming the prognostic value of SCUBE2 in luminal-type breast cancer patients. Here, SCUBE2 is linked to breast cancer.