Appendix

• Rare, usually asymptomatic (Int J Surg Pathol 2009;17:231)
• The majority of appendiceal diverticula are acquired (pseudodiverticula), consisting of mucosa, submucosa and serosa but not muscularis propria
• Congenital diverticula (true diverticula) consist of all layers of the appendiceal wall (Int J Surg Pathol 2009;17:231)
• A meta analysis of 11 studies revealed a strong association between appendiceal neoplasms and appendiceal diverticulosis; however, no significant correlation was found between low grade appendiceal mucinous neoplasm (LAMN) and appendiceal diverticulosis in another study (ANZ J Surg 2020;90:1871, Mod Pathol 2020;33:953)

• ICD-10: K38.2 - diverticulum of appendix

• Uncommon, incidence is ~2% in surgical appendectomy specimens; often underreported due to their small size and asymptomatic nature (Int J Surg Pathol 2009;17:231, ANZ J Surg 2020;90:1871)
• Congenital appendiceal diverticulosis is very rare (incidence of 0.014%) (Int J Surg Pathol 2009;17:231)
• Acquired appendiceal diverticulosis is usually seen in older patients (> 30 years old); M > F (Int J Surg Pathol 2009;17:231, ANZ J Surg 2020;90:1871)

• Appendiceal diverticula are diagnosed microscopically on appendectomy specimens
• Appendiceal diverticula can be identified radiologically; however, detection is usually difficult due to their small size and superimposed inflammation

• Computed tomography (CT) can detect diverticula as round cystic outpouchings of the appendiceal wall and may outperform colonoscopy and barium enema for detecting diverticula (World J Gastroenterol 2021;27:4441)
• Compared with typical acute appendicitis, appendiceal diverticulitis tends to exhibit a larger diameter, periappendiceal fat stranding and extraluminal fluid on CT (Jpn J Radiol 2017;35:225)

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• Risk factors associated with acquired appendiceal diverticula include age > 30 years old, cystic fibrosis and Hirschsprung disease (Int J Surg Pathol 2009;17:231)
• Association between diverticulosis and neoplasms (e.g., low grade mucinous neoplasia, sessile serrated lesion, carcinoid tumor and carcinoma) (ANZ J Surg 2020;90:1871)

• 18 year old woman with inflamed congenital diverticulum (J Surg Case Rep 2023;2023:rjad116)
• 19 year old woman with congenital appendiceal diverticulum (Cureus 2021;13:e14488)
• 72 year old man with a 20 mm cecal lesion during a colonoscopy, which turned out to be an appendiceal diverticulum at the appendiceal base (BMC Gastroenterol 2022;22:262)
• 73 year old woman with appendiceal diverticulum associated with chronic appendicitis (Int J Surg Case Rep 2014;5:961)

• Appendectomy is the treatment of choice for symptomatic appendiceal diverticulitis
• Prophylactic appendectomy may be beneficial for appendiceal diverticulosis due to its higher perforation rate, higher mortality rate and association with neoplasm (Am Surg 2006;72:221, ANZ J Surg 2020;90:1871)

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Contributed by Qingqing Liu, M.D., Ph.D.

• Appendix, appendectomy:
  • Appendiceal diverticulosis with associated active chronic diverticulitis

• Appendix, appendectomy:
  • Ruptured appendiceal diverticulum with associated mucin extravasation in the periappendix, inflammation and fibrosis (see comment)
  • Comment: The appendix has been entirely sectioned and reviewed. Negative for dysplasia or neoplasm.

• Appendiceal endometriosis:
   

  • Endometrial glands and stroma with associated hemorrhage or hemosiderin laden macrophages
  • Affects women of reproductive age
  • PAX8, ER and CD10 immunohistochemistry study can help with diagnosis
• Appendiceal mucinous neoplasm:
  • Extrusion of mucin seen in ruptured diverticula can mimic low grade appendiceal mucinous neoplasm (LAMN)
  • However, LAMN is lined by neoplastic epithelial cells with diminished or decreased lamina propria, which should not be identified in diverticula (Am J Surg Pathol 2009;33:1515)

Which of the following is correct regarding the entity shown in the image above?

1. All cases exhibit a higher perforation rate
2. It can be acquired or congenital
3. It is a frequently encountered lesion and is commonly observed in routine surgical specimens
4. It is an insignificant pathological finding; therefore, it does not require reporting

B. It can be acquired or congenital. Answer C is incorrect because the entity is appendiceal diverticulosis, which is a rare finding. Answer D is incorrect because there is a strong association between appendiceal diverticulosis and neoplasms; therefore, reporting of diverticulosis is required. Answer A is incorrect because appendix with acquired diverticulosis (acquired but not all diverticulosis) has a greater likelihood of perforation and mortality when inflamed.

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Reference: Diverticulosis