MUC5B mRNA transcripts were detected in bone marrow aspirates of 9/46 patients (19.5%) who underwent primary tumor resection [11] but not in 36 samples of normal peripheral blood samples, suggesting that MUC5B may be a specific marker with a high specificity (100%) for the diagnosis of breast cancer cell dissemination [10], [11]. This evidence concerns the gene MUC5B and breast cancer.