N64: Peritoneal And Abdominal Wall Metastasis Following Colectomy In A Patient With Lynch Syndrom. Is It Time To Rethink The Non-Metastatic Theory?

P. C. Ambe1, D. Goedde2, G. Möslein3

1 – Department of Visceral-, Minimally Invasive and Oncologic Surgery Marien Hospital Düsseldorf. 2 – Institute of Pathology and Molecular Pathology Helios University Hospital Wuppertal. 3 – Center for hereditary gastrointestinal tumors Helios University Hospital Wuppertal.


Aim: Hereditary non-polyposis colorectal cancer defines the development of colorectal cancer within the spectrum of presentation of Lynch syndrome. A major characteristic of CRC in Lynch individuals is the failure to metastasize despite the large tumor size.  Herein we present a case of metastatic CRC in a patient with a pathogenic MSH2 / MSH 6 mutation.

Method: A 68 year old Caucasian male patient with a history of right nephrectomy 25 years after a  uretheral cancer. Mismatch repair analysis confirmed MSI-H for MSH2 / MSH6. The patient now presented with a rectal cancer and to date he had not been recommended genetic testing. He underwent an anterior rectal resection with a protective loop ileostomy in December 2017 for colorectal cancer of the rectosigmoidal junction (pT3N0pV0pL0G2R0).  An abdominal wall mass was found 10 months after surgery at the former ileostomy site during follow-up, which was completely excised with negative margins. Five months later, computed tomographic scans of the abdomen suspected recurrent metastasis including a peritoneal mass.  Surgical exploration was performed.

Results: The abdominal wall mass was completely removed with negative margins. Equally, limited peritonectomy was performed during the second exploratory laparotomy. Histopathology confirmed the presence of metastasis from a colorectal cancer with loss of MSH 2 / MSH 6 proteins on immunohistochemistry. The patient was discussed at the interdisciplinary oncologic board after which adjuvant checkpoint inhibitor  therapy  was recommended However, the insurance was not willing to pay for this treatment.

Conclusion: Histopathologic features including loss of MSH 2 / MSH6 protein expression on immunohistochemistry in both the primary tumor as well as the metastatic lesions confirms the presence of metastatic seeding. This provides evidence for a metastasis of CRC in a patient with Lynch syndrome and disapproves the currently accepted non-metastatic theory. We conclude, that we cannot rely on the theory and are mandated to adhere to all principles of oncological surgery and also of stringent follow-up.