PAX8 detection is associated with which embryologic structure?

• A. Urogenital sinus
• B. Wolfian ducts
• C. Mullerian ducts
• D. Mullerian eminence

Answer: (C)

PAX8 marks tissues derived from the Müllerian ducts. These paramesonephric ducts are the embryologic structures that develop into the female internal genitalia—fallopian tubes, uterus, cervix, and the upper portion of the vagina. In adults, many Müllerian-derived tissues and tumors (like certain ovarian and endometrial cancers) show PAX8 expression, making it a useful marker of Müllerian lineage. The Wolffian (mesonephric) ducts form male internal genitalia, and the urogenital sinus develops urinary structures, not Müllerian derivatives, so they don’t explain PAX8 detection. The Müllerian eminence is an early precursor related to Müllerian duct formation, but the marker’s association is with Müllerian ducts as the adult lineage.