The distinction of mesonephric duct hyperplasia (MDH) from mesonephric duct remnants is arbitrary. In MDH, the ducts and tubules are larger, irregular, and may have lobular arrangement. Three types of MDH have been described : lobular (shown here), diffuse, and ductal types. Distinction of MDH from mesonephric adenocarcinoma is important. Presence of a mass, clinical symptoms, nuclear atypia, high mitotic activity, vascular invasion and high Ki-67 reactivity support malignancy.