A Case of Incidental Schwannoma Mimicking Necrotic Metastatic Lymph Node from Bladder Cancer.

Retroperitoneal schwannoma is a very rare case of schwannoma which commonly occurs in the other part of the body. However, it is difficult to distinguish schwannoma from other tumors before pathological examination because they do not show specific characteristics on imaging study such as ultrasound, computed tomography (CT), and magnetic resonance image (MRI). A 60-year-old male showed a retroperitoneal cystic tumor which is found incidentally during evaluation of coexisted bladder tumor. Neurogenic tumor was suspicious for the retroperitoneal tumor through pre-operative imaging study. Finally, a schwannoma was diagnosed by immunohistochemical examination after complete surgical excision laparoscopically. As imaging technology is developed, there may be more chances to differentiate schwannoma from other neoplasm. However, still surgical resection and histopathological examination is feasible for diagnosis of schwannoma.