Expression of PAX۲ and PAX۸ in Wilms Tumor: A Tissue Microarray-based Immunohistochemical Study

Background & Objective: There is currently inadequate information about the expression of immunohistochemical markers in pediatric tumors. Paired box genes ۲ and ۸ (PAX۲ and PAX۸) genes have an essential role in kidney organogenesis. This study aimed to investigate the IHC expression of PAX۲ and PAX۸ in Wilms tumor. Such study would be helpful in diagnosis and possibly in differentiation of this tumor from other mimics, especially in those of poorly differentiated type in small needle biopsy specimens.Methods: We performed a cross-sectional study on ۴۵ Wilms tumor cases referred to Bahrami pediatric hospital between ۲۰۰۵ and ۲۰۱۵. Demographic data were collected from medical documents. Sections from related paraffin blocks were provided by the tissue microarray method, and immunohistochemical (IHC) staining was done for PAX۸ and PAX۲.Results: The mean tumor size was ۹.۹۸±۴.۹۵ cm. Favorable histology was seen in ۸۴.۴% of samples. PAX۲ was expressed in ۴۱ cases (۹۱.۱%), and PAX۸ in ۳۷ patients (۸۲.۲%). PAX۲ and PAX۸ expression was mostly seen in both blastemal and epithelial components (۷۷.۸% and ۶۶.۶%), respectively. Tumors with favorable and unfavorable histology did not significantly differ in PAX۲ and PAX۸ expression (P=۰.۶۳۷). We found a statically significant relationship between PAX۸ expression and tumor size (P=۰.۰۳۳). Conclusion: PAX۲ and PAX۸ markers might helpful in diagnosis of Wilms tumor and may differentiate it from other histologically similar kidney tumors. PAX۸ expression may be associated with larger tumor size. Tumors with favorable and unfavorable histology may not be different in PAX۲ and PAX۸ expression.

Keywords:

Immunohistochemistry , PAX۲ , PAX۸ , Wilms tumor