We employed immunohistochemistry and multiplex immunostaining microarrays (MI chips) to assess the expression of MAGE‐A4, PRAME, MAGE‐A1, KK‐LC‐1, and NY‐ESO‐1 in 21 cases of undifferentiated pleomorphic sarcoma (UPS), 26 cases of smooth muscle sarcoma, 28 cases of liposarcoma, 40 cases of osteosarcoma (OS), and 13 cases of chondrosarcoma. The gene discussed is MAGEA1; the disease is osteosarcoma.