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Gastrointestinal Imaging

E2231. Abdominal Schwannomas: Review of Imaging Findings and Pathology

Lee N,  Hruban R,  Fishman E. Johns Hopkins School of Medicine, Baltimore, MD

Address correspondence to N. Lee (nlee54@jhmi.edu)

Background Information: Schwannomas are benign nerve sheath tumors with Schwannian differentiation. Schwannomas have been found at almost every location of the body; however, visceral locations are very rare, and preoperative diagnosis is challenging because they are often confused with other neoplasms. Schwannomas are usually benign, slow-growing, encapsulated tumors. Malignant nerve sheath tumors are frequently associated with von Recklinghausen syndrome or other types of neurofibromatosis. In this exhibit, we present abdominal schwannomas using multimodality imaging including CT, MRI, and FDG PET/CT with pathology correlation.

Educational Goals/Teaching Points: The goal of this exhibit is to review the imaging findings and differential diagnosis of peripancreatic and pancreatic schwannoma and adrenal, retroperitoneal, and small bowel schwannoma on CT, MRI, and FDG PET/CT. We will also review the histopathology of schwannomas.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Pancreatic schwannomas vary in size and location, with the head of pancreas being involved in most cases (40%). More than two-thirds of pancreatic schwannomas undergo degenerative changes, including cyst formation and hemorrhage, leading to a radiologic confusion with more common solid and cystic pancreatic lesions, including neuroendocrine tumors, making a preoperative diagnosis a clinical challenge. Schwannoma of the gastrointestinal (GI) tract is rare and most often seen in the stomach. Although schwannomas are often clinically indolent for many years, complications such as bowel compression and obstruction or bleeding might occur. A GI schwannoma is similar to a gastrointestinal stromal tumor (GIST), and immunohistochemical staining is necessary to confirm the diagnosis. Schwannomas that arise from the adrenal medulla are very rare entities. Most patients do not have any symptoms, and delayed diagnosis results in a significant size at the time of diagnosis. Often, schwannomas from the retroperitoneum, especially in the juxtaadrenal space, can be misdiagnosed when they mimic adrenal lesions. On FDG PET/CT, FDG uptake by an incidental schwannoma may mimic metastatic disease or a malignant tumor. Schwannomas are benign. Virtually all GISTs are positive for c-Kit and DOG1 with a variable expression of CD34 and SMA, whereas schwannomas are negative for c-Kit, DOG1, CD34, SMA, and strongly positive for PS100.

Conclusion: Preoperative diagnosis of an abdominal schwannoma is rare, and, as a result, most are surgically resected; however, it should be included in the differential diagnosis when appropriate to guide treatment plan.