These remnants of the mesonephric duct may be unilateral or bilateral. They are tubular or cystic structures with an epithelial lining and have a layer of smooth muscle (Figure 1 and Figure 2). These must be distinguished from cysts in the region of the ovary, such as bursa cysts. A distended bursa collapses at dissection, disclosing an intact ovary within it. Cysts occurring in the ovary are found within the ovarian parenchyma and can generally be dissected intact. Cysts of the paraovarian tissue are characterized by a large fluid-filled sac in the mesovarium. These cysts are lined by cuboidal to columnar epithelium, surrounded by smooth muscle, and filled with pale-staining eosinophilic flocculent material.
Oviduct - Mesonephric duct remnant should be diagnosed whenever present but need not be graded.
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National Toxicology Program. 2006. NTP TR-533. Toxicology and Carcinogenesis Studies of Benzophenone (CAS No. 119-61-9) in F344/N Rats and B6C3F1 Mice (Feed Studies). NTP, Research Triangle Park, NC.Abstract: https://ntp.niehs.nih.gov/go/20475