Inverted Appendix in a Patient With Weakness and Occult Bleeding

Appendiceal mucinous neoplasms (AMNs) are rare tumors of the appendix that can be asymptomatic or present with acute right lower quadrant (RLQ) pain mimicking appendicitis. Due to their potential to cause either no symptoms or nonspecific symptoms, such as abdominal pain, nausea, or vomiting, AMNs are often found incidentally during appendectomies or, even more rarely, colonoscopies. Most AMNs grow slowly and have little metastatic potential. However, due to potential complications, such as bowel obstruction and rupture, timely detection and removal of AMN is essential. We describe the case of a patient who appeared to have acute appendicitis complicated by rupture on imaging who was found instead to have a perforated low-grade AMN during surgery.

Case Presentation

A male patient aged 72 years with a history of type 2 diabetes mellitus, hypertension, and aortic stenosis, but no prior abdominal surgery, presented with a chief concern of generalized weakness. As part of the workup for his weakness, a computed tomography (CT) scan of the abdomen was performed which showed an RLQ phlegmon and mild fat stranding in the area. Imaging also revealed an asymptomatic gallstone measuring 1.5 cm with no evidence of cholecystitis. The patient had no fever and reported no abdominal pain, nausea, vomiting, or change in bowel habits. On physical examination, the patient’s abdomen was soft, nontender, and nondistended with normoactive bowel sounds and no rebound or guarding.

To manage the appendicitis, the patient started a 2-week course of amoxicillin clavulanate 875 mg twice daily and was instructed to schedule an interval appendectomy in the coming months. Four days later, during a follow-up with his primary care physician, he was found to be asymptomatic. However, at this visit his stool was found to be positive for occult blood. Given this finding and the lack of a previous colonoscopy, the patient underwent a colonoscopy, which revealed bulging at the appendiceal orifice, consistent with an inverted appendix. Portions of the appendix were biopsied (Figure 1). Histologic analysis of the appendiceal biopsies revealed no dysplasia or malignancy. The colonoscopy also revealed an 8-mm sessile polyp in the ascending colon which was resected, and histologic analysis of this polyp revealed a low-grade tubular adenoma. Additionally, a large angiodysplastic lesion was found in the ascending colon as well as external and medium-sized internal hemorrhoids.

Six weeks after the colonoscopy, the patient was taken to the operating room for a laparoscopic appendectomy. Upon entry of the abdomen, extensive adhesions throughout the RLQ were found which required adhesiolysis. A calcified fecalith adherent to the mesentery of the small intestine in the RLQ was also found and resected. After lysis of the adhesions, the appendix and fibrotic tissue surrounding it could be seen (Figure 2). The appendix was dilated and the tip showed perforation. During dissection of the appendix, clear gelatinous material was found coming from the appendiceal lumen as well as from the fibrotic tissue around the appendix. On postoperative day 1 the appendix was resected and the patient was discharged.

Histologic specimens of the appendix were notable for evidence of perforation and neoplasia leading to a diagnosis of low-grade AMN. The presence of atypical mucinous epithelial cells on the serosal surface of the appendix, confirmed with a positive pancytokeratin stain, provided histologic evidence of appendiceal perforation (Figure 3). The presence of nuclear atypia demonstrated that the appendix was involved by a neoplastic process. Additionally, attenuation of the normal appendiceal epithelium, evidence of a chronic process, further helped to differentiate the AMN from complicated appendicitis. The presence of mucin involving the serosa of the appendix led to the classification of this patient’s neoplasm as grade pT4a. Of note, histologic examination demonstrated that the surgical margins contained tumor cells.

Given the positive margins of the resected AMN and the relatively large size of the neoplasm, a laparoscopic right hemicolectomy was performed 2 months later. Although multiple adhesions were found in the terminal ileum, cecum, and ascending colon during the hemicolectomy, no mucinous lesions were observed grossly. Histologic analysis showed no residual neoplasm as well as no lymph node involvement. On postoperative day 3 the patient was discharged and had an uneventful recovery. At his first surveillance visit 6 months after his hemicolectomy, the patient appeared to be doing well and reported no abdominal pain, nausea, vomiting, change in bowel habits, or any blood in the stool.

Discussion

AMNs are rare tumors with an annual age-adjusted incidence of approximately 0.12 per 1,000,000 people.¹ These neoplasms can present as acute or chronic abdominal pain, gastrointestinal bleeding, intestinal obstruction, or acute abdomen.^2-4 Most AMNs, however, are asymptomatic and are usually found incidentally during appendectomies for appendicitis, and can even be found during colonoscopies,such as in this case.^5,6

Low-grade AMNs are distinguished from appendiceal mucinous adenocarcinomas by their lack of wall invasion.⁷ Additionally, low-grade AMNs have a very good prognosis as even neoplasms that have spread outside of the appendix have a 5-year overall survival rate of 79 to 86%.⁸ These low-grade neoplasms also have extremely low rates of recurrence after resection.⁹ In contrast, appendiceal mucinous adenocarcinomas have a much worse prognosis with a 5-year overall survival rate of 53.6%.¹⁰