Retroperitoneal schwannoma mimicking a pancreatic cystic neoplasm: a case report

Abstract

Schwannomas are mesenchymal tumors that arise from differentiated peripheral nerve Schwann cells and are mostly benign in nature. They tend to occur most frequently in the head and neck regions or in the trunk and flexor surfaces of the upper extremities. However, deeply seated schwannomas can arise in the posterior mediastinum and very rarely in the retroperitoneal space. Owing to the anatomic location, broad differential diagnosis, elusive presentation, and lack of specific radiologic and clinical features, retroperitoneal schwannomas can pose a significant diagnostic challenge. Accurate diagnosis of this rare pathology is usually established based on immunohistochemistry and histopathologic examination following surgical resection. We present a case of an elderly gentleman who underwent surgical resection of a presumed pancreatic cystic neoplasm However, final histopathologic evaluation demonstrated a retroperitoneal schwannoma with cystic degeneration. The diagnosis was confirmed through a combination of immunohistochemistry and a comprehensive targeted next generating sequencing assay that analyses 161 genes including those that are known to be commonly mutated in a subset of schwannoma tumors. In this report, we highlight the importance of employing the aforementioned novel molecular techniques to improve diagnostic accuracy for this rare clinical entity and ultimately guide surgical planning and aid in patient counseling.