[Primitive benign retrovesical schwannoma: an extremely rare tumor, a case report].

Schwannoma is usually a benign tumor of nervous origin arising from Schwann sheath cells. It is an extremely rare tumour because of its low incidence and its retrovescical localization. Histological and immunohistochemical examinations confirm the histological type as well as the benign or malignant origin of schwannoma. Because of the risk of recurrence and malignant transformation, excision must be complete. We report the case of a 39 years old patient, hospitalized for chronic pelvic pain accompanied by a sensation of heaviness, lower urinary tract irritation and urinary hesitancy. Diagnostic imaging (ultrasound, CT scan, MRI) of the pelvis showed a left-lateralized retrovescical mass with a thin wall, measuring 68x70x70 mm exerting mass effect on the bladder and the sigmoid. The surgical procedure, a midline laparotomy, allowed the removal of a well encapsulated retrovesical mass. Histological and immunohistochemical examinations concluded to a benign schwannoma. Recidivism and malignant transformation, although rare after surgery, impose postoperative clinical monitoring and annual CT scanning.