Uroplakin is not a Reliable Immunohistochemical Marker for Malignant Mesothelioma of the Pleura

AIM: To analyze the immunohistochemical expression of uroplakin (URO) in pleural malignant mesothelioma (PMM). METHODS AND RESULTS: We analyzed URO expression in PMM using similar immunohistochemical techniques at 2 separate institutions. At an antibody dilution of 1:10, 0/5 PMMs were immunoreactive for URO. At 1:8, diffuse weak cytoplasmic staining was seen in all 38 PMMs tested, but no membrane staining was observed. Adjacent nontumor tissue and positive control tissue showed cytoplasmic staining of equivalent intensity. Similar staining results were observed in 27 PMMs at a 1:5 dilution. CONCLUSIONS: At an antibody dilution for which positive and negative control tissues stain appropriately, PMM does not stain for URO. At higher antibody concentrations, PMM exhibits nonspecific cytoplasmic staining. We assert that URO is not a useful immunohistochemical marker for the detection of PMM. Further studies addressing whether URO is overexpressed at the mRNA level in PMM are warranted.