MSLN and neoplasm: Similar to observations in human ovarian tumors [22,26,52,53], there was limited background stain in normal hen ovary and tumors that did not have mesothelin mRNA expression while there was intense staining of surface epithelial cells, tumor cells and clusters of cells in the ovarian stroma of mesothelin mRNA expressing tumors; cell surface staining was more intense than in the cytoplasm.