Interestingly, in our study, 80% of patients with triple-negative breast cancers had a CAIX expression in lymph-node metastasis above median (CAIX high), compared to 69.2% of the Her2 + subtype and 18.8% of the HR + Her2-negative group (p = 0.003). Here, CA9 is linked to metastatic malignant neoplasm in the lymph nodes.