The diagnosis of EwS can be confidently established in case of high BCL11B immunoreactivity (IRS >6; i.e., moderate nuclear staining intensity in at least 80% of tumor cells, or strong nuclear staining intensity in at least 60% of tumor cells) and/or high GLG1 immunoreactivity (IRS >9; i.e., strong perinuclear staining in at least 80% of tumor cells). The gene discussed is GLG1; the disease is neoplasm.