EPO and neoplasm: Other markers for internal neoplasia (e.g., hormones: erythropoietin, norepinephrine, normetanephrine; enzymes: alkaline phosphatase; antibodies/immunoglobulins: autologous antibodies, monoclonal gammopathy) are the subject of current research [47] and their relevance in cases of intraocular tumors needs to be assessed in the future.