DIFFERENTIAL IMMUNOHISTOCHEMICAL STAINING FOR RETINOBLASTOMA PROTEIN WITH THE ANTIBODIES-C15 AND 1F8 IN MALIGNANT MESOTHELIOMA

The results of an immunohistochemical study of retinoblastoma protein in human non-neoplastic mesothelium (40 cases) and in malignant mesoth elioma (36 cases) using the antibodies 1F8 and C15 are reported. All c ases of malignant mesothelioma and non-neoplastic mesothelium were imm unoreactive in more than 75 % of the mesothelial cells for retinoblast oma protein with the C15 polyclonal antibody. Immunoreactivity for ret inoblastoma protein was virtually absent with the 1F8 monoclonal body in neoplastic cells of all investigated mesotheliomas. In contrast, st romal cells in these mesotheliomas and all cases with non-neoplastic m esothelium were immunoreactive with the monoclonal antibody 1F8 in mor e than 75 % of the cells. These findings may be indicative for the pre sence of an abnormal retinoblastoma protein in malignant mesothelioma lacking an epitope coded for between exons 21-27.