Melanoma-Associated Antigen C2 (MAGE-C2) is often expressed in tumors, including seminomas, melanoma, breast tumors, colorectal carcinomas, prostate cancers, non-small cell lung carcinomas, bladder tumors, hepatocellular carcinomas, head and neck squamous carcinomas, squamous cell carcinomas of the larynx, medulloblastomas, gliomas, multiple myelomas, Hodgkin lymphomas, gastrointestinal stromal tumors, salivary gland carcinomas, esophageal squamous cell carcinomas, in particular in those with features of more advanced disease and poor prognosis. The gene discussed is MAGEC2; the disease is breast neoplasm.