Look mainly for malignancy:
When finding adenocarcinoma in pleural fluid in a female, and there is no other specimen, preferably perform immunostaining including PAX-8 and WT-1 to confirm a Müllerian tract origin. Also consider p53 to distinguish low-grade (wild-type staining) from high grade (aberrant staining) serous ovarian carcinoma.
Comment: Immunohistochemistry was performed, and showed tumor cells positive for PAX-8 and WT-1, and negative (null phenotype) for p53. These findings are consistent with a tumor of Müllerian (serous) origin.