Retroperitoneal Ancient Schwannoma: A Case Report.

Schwannomas are extremely rare tumors that are composed of Schwann cells. Retroperitoneal localization comprises 0.7% to 2.6% of all schwannomas. Patients usually present with nonspecific symptoms. There are no pathognomonic features on radiologic evaluation. Preoperative biopsy is not recommended because of complication risks; however, surgery is necessary for diagnosis and treatment. Although most schwannomas are benign tumors, those that are associated with von Recklinghausen disease are malignant. Schwannomas exhibit regions of high and low cellularity, termed Antoni A and Antoni B areas, with a diffuse positivity of S100 protein on pathologic evaluation. If there are degenerative changes, such as cyst formation, hemorrhage, calcification, and hyalinization, these tumors are termed ancient schwannomas. We present a case of retroperitoneal ancient schwannoma.