We report a case of pseudomyxoma peritonei (PMP) arising in a 62-year-old male patient with Lynch syndrome (LS). The patient's medical history included an adenocarcinoma of the colon for which a right hemicolectomy was performed and a pancreatectomy due to an intraductal papillary mucinous neoplasm (IPMN) with invasive colloid carcinoma. It was considered that the PMP could be a metastasis of the earlier colonic or pancreatic carcinoma. The pancreatic carcinoma, colon carcinoma, and PMP tissues were examined, and immunohistochemical and molecular analyses were performed to determine the PMP origin. Histopathologic examination revealed morphological similarities with the pancreatic colloid carcinoma, and further immunohistochemical and molecular analyses, including a shared GNAS mutation, confirmed the pancreatic origin of the PMP. In conclusion, this is a unique case of a patient with LS presenting with PMP originating from an IPMN with invasive colloid carcinoma, several years after pancreatectomy. The present case has important diagnostic implications. The IPMN should be considered as a rare extracolonic manifestation of LS, and pancreatic carcinoma origin should be considered in patients presenting with PMP. This case report highlights the added value of molecular diagnostics in daily pathology practice.
From the *Department of Pathology, University Medical Center Utrecht, Utrecht; and
Departments of †Pathology and
‡Radiology, St Antonius Hospital, Nieuwegein, the Netherlands.
Received for publication May 25, 2018; accepted October 23, 2018.
Address correspondence to: Wenzel M. Hackeng, BSc, Department of Pathology, University Medical Center Utrecht (H04-312), Heidelberglaan 100, 3584 CX Utrecht, the Netherlands (e-mail: email@example.com).
W.M.H. and L.E.V.M.G. contributed equally to this work.
This study was supported by The Dutch Digestive Foundation (MLDS CDG 14-02).
The authors declare no conflict of interest.