Gastric cancer is a common malignancy in Australia with an estimated 2246 new cases in 2020, representing approximately 1.5% of all new cancer diagnoses (5). The pattern of metastatic spread differs based on the histological subtype but overall, most of the metastatic disease burden involves the liver (48%), peritoneum (32%), lung (15%), and bone (12%) (6). Metastatic spread to the appendix is an exceedingly rare phenomenon with only a handful of cases previously reported in the literature (2, 7–16). These cases have been summarised in Table 1.
The exact mechanism by which gastric cancer metastasises to the appendix is unknown. A hypothesis is that metastases occur via peritoneal dissemination which then infiltrates through the serosa and subsequently through into the appendiceal lumen (9, 15). At some point, this infiltration may cause a perforation, causing clinical acute appendicitis with peritonitis. More research into the specific cellular and genetic mechanisms are required to further clarify the exact mechanism of this.
Clinical staging is critical to determine the management pathway. Diagnosis is often initially through endoscopic examination, biopsies, and confirmation through histopathology. Staging should then be routinely performed with cross-sectional CT imaging of the chest, abdomen, and pelvis assessing for the presence of metastatic disease. If at this point surgical resection is indicated, it is recommended that diagnostic laparoscopy is performed to assess for the presence of peritoneal metastatic deposits before surgical resection of the gastric cancer (16).
In most of the reported cases (70%), the diagnosis was established incidentally secondary to a presentation of presumed simple acute appendicitis. Only after histopathological examination of the appendix specimen was the presence of metastatic gastric cancer revealed. Pina-Oviedo et al (14) described a case where the appendiceal metastasis was discovered through CT staging and confirmed once excised. In another case, Alhadid et al (3) described a patient who underwent a major gastric resection which was then complicated by an internal hernia. This required an extended right hemicolectomy which incidentally identified metastatic cancer within the appendix. Fu et al (10) described a patient who underwent colonoscopy for investigation of anal pain who had previously had a total gastrectomy for gastric adenocarcinoma. Biopsies confirmed metastatic adenocarcinoma to the appendix.
Our case is unique in that, to our knowledge, it is the only case reported where the appendiceal metastasis has been discovered through diagnostic laparoscopy performed just before the planned major gastric resection. As mentioned, the role of diagnostic laparoscopy is a well-established practice, particularly as a method to rule out peritoneal disease burden which is difficult to identify on preoperative cross-sectional imaging (16–18). In this case, the diagnostic laparoscopy upstaged the patient, and the treatment trajectory was altered with a referral to oncology for consideration of chemotherapy. The limitations of preoperative cross-sectional imaging are further demonstrated through this case with several modalities reporting a normal, non-tumorous appendix.