An appendiceal mucocele associated with inverted epithelium and submucosal hyperplasia at the appendiceal root: a rare case report.

A 54-year-old woman was referred to our hospital because of abnormal colonoscopic findings, including a submucosal protuberance at the appendiceal root. A biopsy showed no malignant findings. Computed tomography revealed a 20-mm cystic lesion with thick walls at the appendiceal root, suggestive of an appendiceal mucocele. Laparoscopic ileocecal resection was performed based on the preoperative diagnosis of a suspected mucinous appendiceal neoplasm. The resected specimen showed a closed appendiceal orifice surrounded by a mucus-containing submucosal tumor. Histopathologically, the appendiceal epithelium was circumferentially inverted in the appendiceal root, with hyperplasia of the submucosal connective tissue. No atypical epithelium was observed. We hypothesized that repeated partial invagination of the appendiceal root caused submucosal hyperplasia and drainage disturbance of the appendiceal content, leading to the development of a mucocele.
Competing Interests: Human/animal rightsAll procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008(5).Informed consentInformed consent was obtained from the patient included in the study.Authors’ contributionsAll authors contributed to the study conception and design. Material preparation and data collection were performed by Shuhei Asai, Hideo Miyake, Asayo Kato, Norihiro Yuasa, Rio Takada, and Masahiko Fujino. The first draft of the manuscript was written by Shuhei Asai, and all authors read and approved the manuscript.Conflict of interestThe authors declare that they have no conflict of interest.Funding sourceThis work is supported by Japanese Red Cross Aichi Medical Center Nagoya Daiichi Hospital Research Grant to SK (NFRCH 23-0008). The funder had no role in study design, data collection, data analysis, decision to publish, or preparation of the manuscript.