Immunohistochemical (IHC) assay for immunoglobulin M (IgM) aims to detect the presence and distribution of this type of antibody in tissue samples. It is primarily used as part of an immunological panel to evaluate kidney diseases (nephropathies) such as membranous proliferative nephropathy (MPGN) and some forms of immune-mediated nephritis. It may also be used to evaluate certain lymphoproliferative disorders.