|Year : 2015 | Volume
| Issue : 3 | Page : 341-343
Somnath Gooptu1, Gurjit Singh1, Iqbal Ali1, Mahendra Kataria2
1 Department of General Surgery, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra
2 Department of Surgery, Padmashree. Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra
|Date of Web Publication||15-May-2015|
Department of General Surgery, Padmashree. Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
Schwannomas are rare tumors that arise from the Schwann sheath of nerves. They are commonly seen in the head and neck region and in both extremities. However, retroperitoneal schwannomas are a rare entity. We report a case of a 35-year-old female presenting with a lump in the right lumbar region. She had loss of sensations over the L3-L4 dermatomes. Computerized tomography of the abdomen and pelvis revealed a mass of size 7.1 cm 7.1 cm 8.3 cm posterior to the right psoas muscle extending superiorly to the lower pole of the right kidney with its anterior displacement. There was narrowing of the right L3-L4 neural foramina. The mass was completely excised. It was diagnosed as benign schwannoma on histopathology examination. Post-operatively, the patient had shown recovery. In a 1-year follow-up post resection, the patient has not shown any evidence of recurrence. Most of the schwannomas are benign and hence follow-up is necessary to detect and prevent recurrence.
Keywords: Retroperitoneal mass, retroperitoneal schwannomas, schwannoma
|How to cite this article:|
Gooptu S, Singh G, Ali I, Kataria M. Retroperitoneal schwannoma. Med J DY Patil Univ 2015;8:341-3
| Introduction|| |
Schwannomas are rare tumors that arise from the Schwann sheath of the peripheral or cranial nerves except I and II. Primary tumors of the retroperitoneal region are rare and schwannomas comprise only 1-10% of them.  Schwannomas are derived from the peripheral nerve sheath. They can occur anywhere within the neural tissue but are more commonly seen in the head and neck region and both extremities. They are rarely seen in the retroperitoneal region. Only 0.7% of benign schwannomas and 1.7% of malignant schwannomas are present in the retroperitoneal region.  Here, we describe a case of retroperitoneal schwannoma that was suspected on radiological study.
| Case Report|| |
A 35-year-old female presented to the surgical OPD with complaints of pain in the right lumbar region for the past 10 days, which was associated with occasional vomiting, loose motions and burning micturition. A well-defined lump of size 9 cm 8 cm was palpable in the right lumbar region, which was firm in consistency and ballotable. Pain and touch sensations were diminished over the right L3-L4 dermatomes. No other neurological deficit was observed. Ultrasound of the abdomen and pelvis was suggestive of a well-defined heterogenous mass measuring 7.1 cm 7.5 cm in the right paracolic gutter, displacing the bladder wall medially. A computed tomography (CT) scan of the abdomen and pelvis revealed a well-defined circumscribed mass lesion of size 7.1 cm 7.1 cm 8.3 cm posterior to the right psoas muscle extending superiorly to the lower pole of the right kidney with its anterior displacement and medially abutting multiple lumbar vertebrae, IVC and right common iliac vessels with narrowing of the right L3-L4 neural foramen [Figure 1]. The patient underwent exploratory laparotomy and excision of the tumor. Postoperatively, the patient developed weakness of the flexors and extensors (L3-L4) with loss of sensations over the L3-L4. She showed recovery in the power to Grade IV in the affected group of muscles and improvement in sensation in L3-L4 dermatomes following physiotherapy. Histopathological examination revealed compact areas of spindle cells with hyalinized areas, dilated gaping blood vessels [Figure 2] and Antoni B areas [Figure 3] suggestive of schwannoma. The patient has been followed-up till date for a period of 6 months and there is no evidence of recurrence.
|Figure 1: Computed tomography scan (post-contrast study) suggestive of moderate heterogenous soft tissue density extending superiorly from the lower pole of the right kidney reaching up to the level of sacral ala inferiorly|
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|Figure 2: Spindle cells with hyalinized areas with dilated blood vessels, 10×|
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| Discussion|| |
Schwannomas are slow-growing, benign, encapsulated neurogenic tumors that usually occur between the third and fifth decades of life and have an equal predilection for men and women. It may occur in any organ or nerve trunk with the exception of cranial nerves I and II, which lack the Schwann cell.  Shwannomas are rare benign tumors, accounting for only 1-10% of all primary retroperitoneal tumors.  In a study, it was observed that 94% of the retroperitoneal schwannomas were benign and only 6% were malignant.  These are usually located in the head, neck and flexor surface of the extremities. In the retroperitoneal region, the presence of a schwannoma is a rare entity except in patients suffering from Von Recklinghausen's disease.  The malignant change usually takes place when it is associated with Von Recklinghausen's disease. In our case, there was no association of Von Recklinghausen's disease. Among 764 cases of schwannomas in a study, only 17 cases (2.23%) were of primary retroperitoneal schwannomas.  Among these, 16 cases (94%) were benign schwannomas and one case (6%) was malignant schwannoma. Four tumors (23.5%) were in the nerve roots, as was in our case, which involved the L3 and L4 nerve roots. Localization in deeper structures such as the posterior mediastinum and retroperitoneum is unusual, accounting for only 1-3% of all schwannomas and only 1% of all retroperitoneal tumors. 
Clinical features are vague and non-specific or may be caused by compressing of the nearby organs. However, abdominal pain is reported to be the most common presenting symptom.  Our patient also came with similar complaints. Patients may also present with paraesthesia and neuralgia in the distribution of the affected nerves. Hematuria and bone pain are generally related to infiltration of the surrounding structures in malignant forms.  Our patient had sensory loss in the L3-L4 dermatomes.
Schwannomas are present typically eccentric to the nerve of origin. Retroperitoneal schwannomas show cystic degeneration in up to 60% of cases, while calcification is seen in 23% of cases.  In our case, schwannnoma was present eccentric to the nerve of origin. Imaging studies like ultrasound, CT scan and magnetic resonance imaging (MRI) are useful in localizing and identifying the nature of the tumor mass. Target and fascicular signs are the characteristic radiological features of schwannoma; however, they are not seen frequently in retroperitoneal schwannomas.  The "target sign" is seen on T2-weighted MRI images as a hypointense signal in the center and hyperintense signal in the periphery. "Fascicular sign" is the appearance of fascicular bundles in neurogenic tumors. Hence, we believe that diagnosing a case of retroperitoneal schwannoma in the absence of these characteristic features requires a high index of suspicion. The differential diagnosis of retroperitoneal schwannomas include paraganglioma, pheochromocytoma, liposarcoma and malignant fibrous histiocytoma.  Even with an intraoperative frozen section analysis, the possibility of malignancy cannot be ruled out and hence a definitive diagnosis can be attained only by histopathological and immunohistochemical examinations. The diagnosis of schwannoma can be confirmed by histopathological examination. The two histopathological types include Antoni A and Antoni B types. The "Antoni A" areas are interwoven bundles of bipolar cells in a well-organized, often palisading, pattern. The "Antoni B" areas are loosely textured pleomorphic cells.  In our case, Antoni B cells along with dilated gaping blood vessels were present, which was suggestive of schwannoma. In case of doubt, immunohistochemistry may be resorted to as tumor cells are positive for S-100. 
Complete surgical excision is the treatment of choice for both benign and malignant retroperitoneal schwannomas.  Adjunctive radiotherapy and chemotherapy provide no additional benefits.  Benign schwannomas have a local recurrence rate of 10-20%, which may be due to incomplete surgical excision and hence a conservative approach such as enucleation is not sufficient.  In one study, it was observed that two patients undergoing surgery developed complications.  One patient developed L2-L4 root injury and the other developed L5-S1 nerve impairment, which recovered following physiotherapy. Our patient also developed weakness of the right lower limb associated with L3-L4 sensory loss and had recovered partially after physiotherapy. Local recurrences have been reported even after complete excision and hence a long-term follow-up is mandatory. This patient has been followed-up till date for a period of 6 months without evidence of any recurrence.
| Conclusion|| |
A retroperitoneal schwannoma is a rare disorder and most cases are benign. Complete excision and follow-up is mandatory to prevent and detect recurrence.
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[Figure 1], [Figure 2], [Figure 3]