Carbohydrate antigen which is accumulated in various human cancer tissues and secreted into the blood stream. The carbohydrate moiety can be further modified with fucose or sialic acid. Monoclonal antibodies have been determined which can discriminate each subgroup of this antigen in the sera of cancer patients. Sialyl $SSEA-$1 antigen is particularly elevated in the sera of patients with a variety of tumors.
