Unusual findings in 68 cases of appendiceal diverticulum: Accompanying neoplastic lesion should be kept in mind

Abstract

Purpose: Congenital and acquired diverticula of the appendix are very rare and may be associated with a variety of lesions. In this study, we aimed to evaluate the cases of the appendiceal diverticulum (AD) in terms of histopathological features and accompanying neoplastic and non-neoplastic lesions. Methods: A retrospective analysis of the appendectomy specimens between January 2007 and June 2022 was performed. All of the cases with AD were reviewed and slides of all cases were re-examined by two pathologists, one of whom was highly experienced in gastrointestinal pathology. The cases were evaluated in terms of age, gender, histopathological features, accompanying neoplastic and non-neoplastic lesions, presence of periappendicular mucin, and misdiagnosis. Results: There were a total of 68 AD cases with 32 (47%) males and 36 (53%) females. The mean age was 54,1 years (24-93). Diverticulitis was seen in 44 cases (64,7%). In 28 (41,1%) cases ADs were accompanied by other lesions such as low-grade appendiceal mucinous neoplasm (LAMN, n=13), endometriosis (n=4), well-differentiated neuroendocrine tumor (n=3), sessile serrated adenoma (SSA, n=3), adenocarcinoma (n=2), LAMN and WD-NET (n=1), granular cell tumor (n=1), and hyperplastic polyp with inflammatory fibroid polyp (n=1). Periappendiceal acellular mucin deposition was seen in 23 (33,8%) cases with associated diverticulitis in 12 of them. In 7 of the 13 cases of LAMN there was mucin accumulation. AD was incidentally found in 15 appendectomies performed during other surgeries. Although defined macroscopically in 8 cases, the diagnosis of AD was missed during the microscopical examination. Conclusion: The probability of detecting a neoplastic lesion in cases with AD is quite high as proven in our study. Therefore, the entire appendix can be sampled in these cases. It is important to pay attention to macroscopic definitions in order not to miss a possible diverticulum in all cases with microscopic perforation and dense inflammation. The close association between LAMN and AD should be kept in mind.