The OSNA assay is globally used in patients with breast cancer not only to detect lymph node metastasis in order to determine whether axillary dissection should be performed but also to predict axillary lymph node metastasis and prognosis from the total tumor load of the total CK19 mRNA expression in a few sentinel lymph nodes [16–25]. Here, KRT19 is linked to metastatic malignant neoplasm in the lymph nodes.