P53 which is a nuclear phosphoprotein has functions like cell differentation, DNA synthesis and repair half-life of P53 which is a tumor supressor gene, is short so that it can only be detected immunohistochemically when ever genetic alterations occurs. Mutant forms are detected in breast, lung, liver, colon, uterus, brain, bladder, ovary, testis and stomach cancers.

In this study, the immunohostochemical staining pattern of P53 in malignant and benign mesothelial cells were evaluated. The cases were collected from the archives of Akdeniz University Medical Faculty, Pathology Department between 1981-1996 years, in the 15 benign mesothelioma cases there were no P53 immunoreactivity in mesothelial cells, but all 14 malignant mesothelial cases were stained. Therefore, whenever there is difficulty in difeerential diagnosis of benign and malignant mesothelial cells, detection of mutant P53 can be helpful with morphology and clinical findings, but the absence of immunoreactiviy can not exclude neoplasia diagnosis.