Retroperitoneal schwannomas: diagnostic and therapeutic implications.

Schwannomas are a rare group of soft-tissue tumors deriving from the peripheral nerve sheath. They can occur anywhere in neural tissue where Schwann cells are present but are most common in the head and neck region and upper and lower extremities. Schwannomas rarely develop in the retroperitoneum but if they do, they can grow to a large size, sometimes displacing, and more rarely invading, surrounding structures and organs before becoming clinical apparent. A correct preoperative diagnosis is difficult to make and these tumors are often misdiagnosed as other soft-tissue lesions occurring in the retroperitoneum. We describe our clinical experience with 4 patients undergoing surgical excision of retroperitoneal schwannomas and review the relevant literature. Materials and methods A 69-year-old woman presented with continuous mild pain in the lower quadrants of the abdomen and a history of weight loss. CT scan showed a well-defined cystic round mass of 7 × 6 × 4 cm in the vicinity of the pancreatic tail; the picture was suggestive of a large cystic tumor of the pancreas. At exploratory laparotomy, a left adrenal mass without infiltration of the pancreas was found and an adrenalectomy was performed. The histological pattern and positive staining for S-100 were consistent with the diagnosis of schwannoma, with normal, non-infiltrated adrenal tissue; cytoplasmic deposition of melanin was characteristic of the melanotic subtype. At 65 months from the diagnosis, the patient is alive with no evidence of relapse. A 66-year-old woman complained of vague digestive disturbance with subcontinuous pain in the left hypochondrium radiating to the back. Ultrasonography (US) and magnetic resonance imaging (MRI) showed a round, expansive left retroperitoneal lesion of 11 × 7 × 7 cm in contact with the aorta, the transverse colon, and the first jejunal loop, but the site of origin could not be recognized (Figures 1A and 1B). At surgical exploration, a large encapsulated heterogeneous mass was found, splitting the leaves of the left psoas muscle; it was easily dissectible from the adjacent structures (Figures 1C and 1D). Pathological and immunohistochemical evaluation revealed a typical benign schwannoma with an expansive growth pattern. Fourteen months after the operation, the patient is asymptomatic with no radiological evidence of recurrent disease. A 51-year-old man was referred to our unit after an episode of nocturnal perspiration associated with shivers and nonspecific abdominal pain. US and CT scan demonstrated a huge neoplasm in the right retroperitoneum very close to the kidney, probably arising from the right adrenal gland (Figures 2A and 2B). At surgery, a 10-cm round mass was found with no signs of infiltration of the right kidney, so the mass was excised en bloc with the adrenal gland (Figures 2C and 2D). At microscopic examination, the adrenal gland was clearly separated from the mass and nervous structures including Schwann cells were evident. Furthermore, the specimen tested positive for S-100 protein, thus confirming the diagnosis of schwannoma. After 17 months, the patient is doing well and CT scan shows no signs of local or distant recurrence.