Cysts are rarely found in the walls of rat vaginas (Figure 1, Figure 2 and Figure 3). These are usually lined by stratified squamous epithelium and filled with keratin and cellular material, which may have inflammatory debris. These cysts are dilated, fluid-filled structures with an epithelial lining. They may have a smooth muscle wall (mesonephric duct remnant) and also may have squamous metaplasia and/or keratinization. Cysts must not be confused with abscesses, which are predominantly filled with neutrophils in various stages of degradation and do not have an epithelial lining.
National Toxicology Program. 1994. NTP TR-442. Toxicology and Carcinogenesis Studies of p-Nitrobenzoic Acid (CAS No. 62-23-7) in F344/N Rats and B6C3F1 Mice (Feed Studies). NTP, Research Triangle Park, NC.Abstract: https://ntp.niehs.nih.gov/go/6028