187 GATA3 Expression Patterns in Human Fetal Mesonephros: A Developmental Basis for Its Role in Mesonephric Adenocarcinoma

Introduction/Objective Mesonephric adenocarcinoma (MA) of the cervix is a rare malignancy of the female genital tract. GATA3 has emerged as a useful immunohistochemical marker for MA; however, most evidence regarding its mesonephric origin stems from animal studies. This study aims to evaluate GATA3 nuclear expression in human fetal mesonephros (HFM) to support its role as an early biomarker of mesonephric differentiation. Methods/Case Report Six fetal mesonephroi (gestational ages 6–10 weeks) were examined using GATA3 immunohistochemistry. OCT3/4 staining was also performed in one 10-week specimen to evaluate gonadal transition. GATA3 expression was assessed in stromal, tubular, and glomerular components. Results Strong nuclear GATA3 staining was identified in peri-renal stromal cells, distal-like tubules, and glomerular mesangial cells in 5 of 6 mesonephroi (6–10 weeks gestation). In the sixth specimen (10 weeks), OCT3/4 highlighted a cluster of stem cells consistent with early male gonadal transition. In this case, GATA3 expression was reduced in both stromal and tubular components of the residual mesonephros. Conclusion GATA3 is expressed in multiple compartments of the early human mesonephros, supporting its utility as a biomarker for mesonephric lineage and mesonephric adenocarcinoma. The diminished expression observed in transitional male mesonephros suggests a potential developmental basis for the rarity of mesonephric adenocarcinoma in male patients