Primary Mucinous Adenocarcinoma of the Vermiform Appendix with High Grade Microsatellite Instability

Abstract

Primary adenocarcinoma of the vermiform appendix is a rare entity and is frequently discovered by the pathologist following appendectomy for suspected appendicitis.We present a 42-year-old male with primary mucinous adenocarcinoma of the appendix initially presenting symptoms of acute appendicitis. Histological investigation of the appendectomy specimen showed a mucinous adenocarcinoma and the patient was treated by secondary right hemicolectomy giving the final histopathological classification of an UICC IIIC tumor. Since the patient fulfills the revised Bethesda criteria analysis of immunoreactivity of DNA mismatch repair proteins was performed showing loss of MLH1 and MSH2 expression associated with high microsatellite instability (MSI-H), not yet reported for primary mucinous appendiceal carcinoma. Further genetic analysis for DNA mismatch repair gene mutations were negative. The patient received intensified adjuvant chemotherapy according to the FOLFOX-4-scheme, since MSI-H colorectal carcinomas might show lower response rates following standard 5-FU-based adjuvant chemotherapy.

High-level Microsatellite Instability in Appendiceal Carcinomas

“…These included: 1) pT1 N0 moderately differentiated adenocarcinoma with loss of MSH2/MSH6 expression and MSI-high by PCR, in a 29-year-old man with Lynch syndrome due to germline A636P MSH2 mutation, 25 2) moderately differentiated colonic-type adenocarcinoma with loss of MSH2/MSH6 expression, confined to the appendix, in a 26-year-old woman with a history of synovial sarcoma, 27 3) invasive adenocarcinoma arising from a sessile serrated polyp, with loss of MLH1 expression in both the adenocarcinoma and polyp but MSI-high by PCR only in the carcinoma component, 29 and 4) pT4a pN2a invasive mucinous carcinoma with MSI-high by PCR and loss of both MLH1 and MSH2 expression, in a 42-year-old man without a family history of cancer. 26 (The appendiceal serrated adenoma was MSI-high with allelic shifts in 3 of 5 microsatellite markers, but no immunohistochemistry or mutational testing of individual MMR genes was performed. 28 ) These cases and other reported investigations of MSI in appendiceal tumors are summarized in Table 2.…”

“…20, 22, 23, 24 To our knowledge, only four individual cases of MSI-high appendiceal carcinomas and one case of an appendiceal serrated adenoma with MSI have been previously reported. 25, 26, 27, 28, 29 Only one of these patients had documented Lynch syndrome. 25 …”

Primary Mucinous Adenocarcinoma of Appendix: A Rare Case Report

“…Therefore, preoperative recognition of adenocarcinoma is not possible and is usually diagnosed after histopathological evaluation of specimens after removal of suspected appendicitis. (2)(3)(4) In our institution, two appendiceal neoplasms have been reported among 2043 appendicectomy specimens in the last two years. One is carcinoid and the other is mucinous adenocarcinoma.…”

Minor salivary gland mucinous adenocarcinoma of buccal mucosa – and review of the literature

“…In the treatment of patients in stage I surgery is the method of choice, in stages II and III surgery combined with chemotherapy, whereas in stage IV surgery combined with chemo/radiotherapy is indicated [10][11][12][13]. Based on the current literature, we conclude that the best treatment modality in patients with MAC of the head and neck region is surgery, comprising wide excision of the tumour with concomitant neck dissection.…”