Schwannomas are tumors that develop from Schwann cels in the peripheral nerve sheaths. They are typically benign and most commonly found in the head, neck, and extremities. However, they can also appear in rare locations such as the retro-peritoneal area, which accounts for only 3% of all schwannomas and 4% of all retroperitoneal tumors .
Although schwannomas are usually benign, malignant forms have been observed in up to 60% of patients with Von Recklinghausen's disease. In this case report, a patient presented with chronic left flank pain that gradually worsened over time. An abdominal CT scan revealed a retroperitoneal mass with clear borders. The patient underwent complete surgical removal of the mass, and an anatomo-pathological examination confirmed that it was a Retroperitoneal Schwannoma (RSS).
This case highlights the importance of considering this rare diagnoses in patients with chronic symptoms, as well as the effectiveness of surgical excision as a treatment for RSS.
A 54-year-old women patient, with no noticeable medical or surgical history, presented with a one-year history of chronic left flank pain, physical examination was unremarkable. Abdominopelvic CT scan was performed and showed a well-circumscribed, heterogenous hypodense retroperitoneal mass developed in the lombo-aortic area, medial to the left kidney measuring 4 x 7 cm (Figure 1).
The mesenteric fat, abdominal organs and muscles were well preserved.
After contrast administration the mass showed a poorly and inhomogeneous contrast enhancement (Figure 2).
Laboratory tests including tumor markers and urine catecholamine were normal. The patient underwent a laparotomy surgery, showing a rounded mass connected to the intervertebral foramina, a complete resection of the tumor was performed.
Pathological examinations revealed a benign schwannoma. The patient made an uneventful recovery, he remained asymptomatic, with no recurrence at a one-year follow-up.
Schwannomas are neurogenic tumors that originate from Schwann cells of peripheral nerve sheaths and are most commonly found in females aged from 20 to 60 years . Although they typically arise from sensory nerves, they can also originate from motor nerves. These tumors most frequently occur in the head and neck region and extremities and are usually benign, with malignant transformation being rare except in cases associated with von Recklinghausen's disease . Retroperitoneal schwannomas, which account for a small percentage of all schwannomas, are typically slow-growing, solid masses with a smooth surface and may exhibit cystic degeneration and hemorrhage .
Radiologic examinations, particularly CT scans with contrast, play a crucial role in diagnosis and reveal well-defined tumors with slightly lower density than surrounding soft tissue, with up to 66% of retroperitoneal schwannomas exhibiting cystic changes. Other degenerative changes, such as calcification, hemorrhage, and hyalinisation, may also be present [4,5].
MRI is considered to be a more effective diagnostic tool than CT in identifying the margins and determining the nerve origin of schwannomas [4,6]. In MR images, schwannomas are typically hypointense on T1 and hyperintense on T2-weighted scans. While two characteristic features of neurogenic tumors on MRI are the "target sign" (a hypointense center with a hyperintense periphery) and the "fascicular sign" (bundles), these features are not commonly observed in retroperitoneal schwannomas . Malignant schwannomas tend to have irregular contours, mixed intensity on both T1- and T2-weighted images, and show signs of invading other structures. However, malignant schwannomas are rare in patients without a history of neurofibromatosis.
In addition to retroperitoneal schwannomas, other neurogenic tumors such as paraganglioma and pheochromocytoma, as well as non-neurogenic tumors like liposarcoma and malignant fibrous histiocytoma, may present with similar findings on both CT and MRI scans. This makes it difficult to make a definitive preoperative diagnosis. Furthermore, if the retroperitoneal schwannoma contains a significant amount of cystic degeneration, other retroperitoneal cystic masses such as hematoma and lymphangioma should also be considered as potential diagnoses.
The definitive diagnosis of retroperitoneal schwannoma is made through histopathologic examination of the collected specimens. In cases where retroperitoneal schwannoma is suspected, wide surgical resection is recommended .
Recurrence of benign schwannoma is rare, and is typically associated with incomplete resection. According to reports, recurrence is observed in only 5%-10% of cases.
Retroperitoneal schwannomas are rare benign tumors. They can be malignant, especially when associated with neurofibromatosis. The final diagnosis is based on histological and immunohistochemical findings of the specimens and the gold standard for its managing is complete surgical resection. Despite the rare location of schwannoma in the retroperitoneum, they should be considered in cases of retroperitoneal abdominal masses.