DIAGNOSTICUM FOR MAMMARY CANCER

PURPOSE:To obtain a mammary cancer imaging agent having high accumulating properties on mammary cancer and possibility of grasping function or multiplication ability of mammary cancer, comprising a radioisotope labeled antibody against estriol-3-sulfate. CONSTITUTION:A protein complex of an estriol-3-sulfate shown by the formula (A is =N-O- or -O-CO-; n is 1-4: -NH-P is residue after removal of one amino state hydrogen atom from protein) at the 6-position is parenterally administered to an organism of vertebrate, an antibody is produced in the organism, then humors (e.g., blood) are collected from the organism and optionally impurities are removed from the humors to give an antibody against the estriol-3-sulfate, a metabolite of estrogen. The antibody is labeled with a radioisotope (I-131, I-132, Ga-67, Ga-68, Tl-201, In-111 or Te-99m) by a well-known method to give the aimed mammary cancer imaging agent.