Image features and clinical analysis of retroperitoneal pelvic schwannoma: a case report

Abstract

Background: Schwannomas are benign usually encapsulated nerve sheath tumors derived from the Schwann cells, and affecting single or multiple nerves. The tumors commonly arise from the cranial nerves as acoustic neurinomas but they are extremely rare in the pelvis and the retroperitoneal area. Retroperitoneal pelvic schwannomas often present with non-specific symptoms leading to misdiagnosis and prolonged morbidity.

Case presentation: We report the case of a 59-year-old woman presenting with a feeling of heaviness in the lower abdomen who was found to have a retroperitoneal pelvic schwannoma originating from the right femoral nerve. She had a history of two resections of peripheral schwannomas at four different sites of limbs. After conducting magnetic resonance imaging, this pelvic schwannoma was misdiagnosed as a gynecological malignancy. The tumor was successfully removed by laparoscopic surgery. Pathological analysis of the mass revealed a benign schwannoma of the femoral nerve sheath with demonstrating strong, diffuse positivity for S-100 protein.

Conclusions: Although retroperitoneal pelvic schwannoma is rare, it should be considered in the differential diagnosis of pelvic masses, especially in patients with a history of neurogenic mass or the presence of neurogenic mass elsewhere.

Keywords: Femoral; Pelvic; Retroperitoneal; Schwannoma.

Fig. 1

The transvaginal ultrasound at diagnosis. a and b A well-defined, hypoechoic mass is in the right adnexa, adjacent to the bladder. c Color Doppler image shows the mass contains internal flow. BL bladder

Fig. 2

Ultrasound shows a solid mass in the deep muscle of right thigh suspiciously originating from the nerve. a The mass is located 1.9 cm away from the thigh surface. b Doppler flow can be detected in the mass

Fig. 3

The MRI reveals a round mass in the pelvis (arrow). a Hypointense on T1. b Hyperintense but heterogenous on T2. c Hyperintense on diffusion-weighted imaging. d The solid part of the mass with obvious contrast-enhancement. MRI magnetic resonance imaging

Fig. 4

The trunk PET/CT examination confirm the presence of the pelvic mass and the lesion in the right thigh muscles. a and b Both the pelvic mass (thick arrow) and the mass in the right thigh (thin arrow) show high tracer uptake. PET/CT positron emission tomography and computed tomography

Fig. 5

Laparoscopic procedure. a Encapsulated solid mass in the retroperitoneal pelvis. b The mass was removed intact

Fig. 6

Histopathologic examination of the benign schwannoma. a × 200. b Strong immunohistochemical positivity for S-100 protein