To test the expression and localization of active SMC1A (pSMC1A) in breast tumors, we used histological sections of the breast cancer spectrum (from tissue microarray) and histological slides of TNBC sections including metastatic (lymph nodes or lung metastases originating from breast cancer), invasive ductal (IDC), lobular carcinoma (ILC) and normal or adjacent normal breast tissues. Here, SMC1A is linked to breast lobular carcinoma.