Two Identical Cases of Extreme Fistulation of Buttocks Originating from a Mesorectal Cyst with Keratinizing Squamous Epithelium: A Novel Clinical Entity

Background: Fistulation in the buttock area are mostly of cryptogladular origin, associated with pilonidal sinus or caused by an underlying disease, e.g. Crohn’’s disease. Several other rare conditions may cause such Fistulation. This paper describes two identical cases that did not fit with any of these differential diagnoses. Patients: Two patients are described that suffered from persistent extensive Fistulation in the perianal and buttock region. Details on the history or the condition, comorbidity, treatments, imaging, pathology and laboratory findings, both previous and during final treatment, were retrieved from the notes. Results: Both patients had a retrorectal cyst lined with keratinizing stratified squamous epithelium and an extensive mesh of fistula tracts on the buttock with the same epithelial lining. Both were cured by excision of the cyst and epithelialised tracks. Discussion: The condition of these two patients is compared with the diseases know to cause fistular disease and the various types of retro rectal cysts. Conclusion: condition described appears to be a separate clinical entity. The cyst and fistulation appear to require complete excision of the structures lined with stratified squamous epithelium for definitive treatment.