Differential Expression of PAX8, WT1, and Calretinin in Peritoneal Cytology: An Immunohistochemical (IHC) Study of Metastatic Ovarian Serous Carcinoma (OSC)
RM McKnight, C Cohen, MT Siddiqui. Emory University Hospital, Atlanta, GA
Background: Metastases from primary ovarian neoplasms are common in peritoneal fluid. Microscopic evaluation has prognostic value as ovarian tumor staging incorporates the presence of malignant cells in peritoneal cytology. Reactive mesothelial cells can mimic OSC, and it is often difficult to distinguish the two on morphology alone. Calretinin by IHC has been recognized as a reliable marker for mesothelial cells, while, WT1 has proven useful in the diagnosis of OSC. This can be a diagnostic pitfall, as mesothelial cells can show immunoreactivity for WT1. Recently, PAX8 has been used as a marker in distinguishing ovarian from mammary carcinoma. To our knowledge no studies using PAX8 have been performed on peritoneal cytology specimens, and its expression in metastatic OSC has not been studied.
Design: IHC for PAX8, WT1, and Calretinin were performed on paraffin-embedded cell block sections from forty-one metastatic OSC peritoneal cytology cases and ten negative controls. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the cytology results were calculated using histological diagnosis as the gold standard. Differential expression of PAX8, WT1, and Calretinin was also evaluated in background mesothelial cells.
|OSC cases||37/41 (90%)||38/41 (93%)||0/41 (0%)|
|Negative controls||0/10 (0%)||10/10 (100%)||10/10 (100%)|