Urothelial Rests, Incidental Finding in a Patient with Acute Appendicitis: A Case Report and Literature Review.

Background: Urothelial rests, also known as Walthard rests, are benign nests of epithelial cells that most often are found in the female gynecologic tract. Only four of these urothelial rests have been described in the appendix. Case report: A 10-year-old female underwent an appendectomy for appendicitis. Histologically, there was acute appendicitis, and an incidental urothelial rest was identified, confirmed by immunostains positive for p63, CK7, and negative for synaptophysin. CD34 highlighted a rim of endothelial cells. Conclusion: Urothelial rests, which often appear in the female gynecologic tract, can occur in other sites such as the appendix. These benign lesions require differentiation from neuroendocrine lesions. The rim of endothelial cells in our report supports a vascular migrational origin.