Treatment of AMNs depends on the extent of their spread. Neoplasms that are confined to the appendix can typically be treated with appendectomy alone, while those that have spread beyond the appendix may require cytoreductive surgery and chemotherapy, namely, hyperthermic intraperitoneal chemotherapy (HIPEC), in addition to appendectomy.11 Cases in which neoplasms are not confined to the appendix also require more frequent surveillance for recurrence as compared to appendix-restricted neoplasms.11
Appendiceal inversion is a rare finding in adults with an estimated prevalence of 0.01%.6 Not only is appendiceal inversion rare in and of itself, it is even more rarely found in combination with appendiceal neoplasms.6 Other causes of appendiceal inversion include intussusception, acute appendicitis, appendiceal nodule, or even iatrogenic due to appendectomy.12-14 While appendiceal inversion can be completely benign, because these morphological changes of the appendix can resemble a polyp, these lesions are often biopsied and/or resected.15 However, lesion resection may be quite problematic due to high risk of bleeding and perforation.15 In order to avoid the risks associated with resection of a potentially benign finding, biopsy should be performed prior to any attempted resection of inverted appendices.15
Another interesting aspect of this case is the finding of fecal occult blood. The differential for fecal occult blood is quite broad and the patient had multiple conditions that could have led to the finding of occult blood in his stool. Hemorrhoids can cause a positive result on a fecal occult blood test (FOBT) although this is relatively uncommon, and hemorrhoids are more likely to cause frank blood to be seen.16 The sessile polyp found in the patient’s colon may also have caused the FOBT to be positive. This patient was also found to have an angiodysplasia (a finding that is associated with aortic stenosis, which this patient has a history of) which can also cause gastrointestinal bleeding.17 Lastly, AMNs may also cause gastrointestinal bleeding and thus a positive FOBT, although bleeding is a relatively uncommon presentation of AMNs, especially those that are low-grade as in this case.18
This case also highlights the association between appendiceal neoplasms and colonic neoplastic lesions. Patients with appendiceal neoplasms are more likely to have colonic neoplastic lesions than patients without appendiceal neoplasms.19 Studies have found that approximately 13 to 42% of patients with appendiceal neoplasms also have colonic neoplastic lesions.19 The majority of these lesions in the colon were right-sided and this finding was also seen in this case as the patient’s polyp was located in the ascending colon.19 Due to this association between appendiceal and colorectal neoplasia, the American Society of Colon and Rectal Surgeons strongly recommends that patients with appendiceal neoplasms or who are suspected of having them receive a colonoscopy.19
Additionally, perforation of an AMN, as was seen in this case, is a finding that should raise significant concern. Perforation of an AMN allows for the spread of malignant mucinous epithelial cells throughout the abdomen. The finding of extensive adhesions throughout the patient’s RLQ was unexpected as abdominal adhesions are most often seen in patients with a history of abdominal surgeries. Considering the lack of any prior abdominal surgeries in this patient, these adhesions were most likely the result of the spread and proliferation of malignant mucinous epithelial cells from the perforated AMN in the RLQ.20 The adhesiolysis performed in this case was thus not only important in order to visualize the appendix, but also for preventing future complications of abdominal adhesions such as bowel obstruction.20 Perforated AMN is also so concerning because it can potentially lead to pseudomyxoma peritonei—a condition in which malignant mucinous epithelial cells accumulate in the abdomen.21 Pseudomyxoma peritonei is extremely rare with an incidence of approximately 1 to 2 cases per million per year.22 Early recognition of AMNs and surgical referral are critically important as pseudomyxoma peritonei is difficult to treat, has a high rate of recurrence, and can be fatal.23
Lastly, this case highlights how findings of a ruptured appendix and/or mucin surrounding the appendix on imaging should warrant laparoscopy because only pathologic analysis of the appendix can definitively rule out AMNs. The utility of laparoscopic evaluation of the appendix is especially apparent as nonsurgical treatment of appendicitis using antibiotics is gaining favor for treating even complicated appendicitis.24 Appendicitis is much more common than AMNs. However, had the patient in this case only been given antibiotics for his suspected complicated appendicitis without any colonoscopy or appendectomy, the neoplasm in his appendix would have gone undetected and continued to grow, causing significant complications. The patient’s age at presentation in this case also necessitated laparoscopic evaluation of the appendix as the incidence of AMNs is highest among patients aged > 60 years.25 Additionally, because appendiceal inversion may be seen with AMNs,the patient’s inverted appendix seen during his colonoscopy was another compelling reason for laparoscopic evaluation of his appendix.6
Conclusions
AMNs can present with nonspecific symptoms or can be completely asymptomatic and are often found incidentally during colonoscopies or appendectomies for acute appendicitis. While it is true that AMNs have low metastatic potential and grow slowly, AMNs can rupture leading to pseudomyxoma peritonei or even cause bowel obstruction warranting timely identification and removal of these neoplasms. Laparoscopic evaluation in cases of ruptured appendices is critical not only for treatment, but also for determining the presence of a potential underlying appendiceal malignancy. Although AMNs are a rare pathology, physicians should still consider the possibility of these neoplasms even when imaging findings suggest appendicitis. Having AMNs as part of the differential diagnosis is especially necessary in cases, such as this one, in which the patient has appendiceal inversion, is aged > 50 years, and has concurrent colorectal neoplasms.