Appendiceal Mucosal Schwann Cell Proliferation Associated with Incidentally Detected Goblet Cell Adenocarcinoma of Appendix in a Case of Invasive Adenocarcinoma of Sigmoid Colon- A Case Report

Abstract Introduction/Objective Appendiceal mucosal Schwann cell proliferation has been suggested to be a putative histologic marker of appendiceal diverticular disease. Appendiceal Goblet cell adenocarcinoma, (GCA) is amongst the most rare appendiceal tumors with a reported incidence of 0.05 cases per 100,000 population per year in United States. They have features of both neuroendocrine tumors and adenocarcinomas, but behave more similarly to adenocarcinomas. Methods/Case Report Herein, we report a case of appendiceal mucosal schwann cell proliferation associated with incidentally detected Goblet cell adenocarcinoma of appendix in a known case of invasive adenocarcinoma of sigmoid colon. A 75-year-old female presented with sigmoid colon obstruction. Intraoperatively, she was found to have gangrenous and perforated colon, as well as a large obstructing sigmoid mass, and underwent total abdominal colectomy with end-ileostomy. On gross examination, a tan bosselated tumor (up to 3.5 cm) was seen in proximal sigmoid colon. Microscopic examination showed Invasive adenocarcinoma, moderately-differentiated. Appendix was unremarkable on gross examination. Incidentally, the appendix microscopically demonstrated “Goblet cell adenocarcinoma”, histologic grade 1 out of 3 (pathologic stage pTis pN0), present in multiple foci within lamina propria of the distal third of appendix over an area measuring 1.5 cm. Additionally, there were foci of SOX10-positive bland- looking spindle cell proliferation in lamina propria of the appendix. This proliferation is rendered as “Schwann cell proliferation”. Results (if a Case Study enter NA) NA Conclusion One study found that “Schwann cell proliferation” is seen in 42% of appendiceal diverticula cases. It has never been reported in association with “Appendiceal GCA” before. Here we report an intriguing case of Schwann cell proliferation associated with this rare entity of GCA for the first time in literature. Therefore, awareness of such coexistence of these pathologic entities in the same appendix is essential to alert the pathologist to look for GCA, whenever Schwann cell proliferation is encountered in random section of an appendix. This case also emphasizes the importance of being vigilant of the possible presence of other tumors in a specimen with a known tumor.