|Year : 2015 | Volume
| Issue : 1 | Page : 47-50
A case of retroperitoneal schwannoma and review of literature
Tozo Luwang Thiyam, Cliff Anderson Wanniang, Aribam Devadutta Sharma, Manihar Singh Haobam
Department of Surgery, Regional Institute of Medical Sciences, Imphal, Manipur, India
|Date of Web Publication||17-Jun-2015|
Dr. Tozo Luwang Thiyam
Lairik Yengbam Awang Lekai, Imphal East - 795 010, Manipur
Source of Support: None, Conflict of Interest: None
The term schwannoma(also known as neurilemmoma) refers to a tumor in which the cells are derived from the neurilemma or the nerve sheath, more commonly referred to as the sheath of Schwann. A retroperitoneal location accounts for 0.3-3.2% of all primary schwannomas and 0.3-6.0% of all retroperitoneal tumors. We report the case of a 47-year-old female with a benign retroperitoneal schwannoma as a rare one.
Keywords: Benign, Schwannoma, Retroperitoneal schwannoma, Tumor
Key Messages: Retroperitoneal schwannoma is rare; its preoperative diagnosis is not always possible and complete excision of it is challenging in view of the complex retroperitoneal anatomy
|How to cite this article:|
Thiyam TL, Wanniang CA, Sharma AD, Haobam MS. A case of retroperitoneal schwannoma and review of literature. J Med Soc 2015;29:47-50
| Introduction|| |
The term schwannoma (also known as neurilemmoma)refers to a tumor in which the cells are derived from the neurilemma or the nerve sheath, more commonly referred to as the sheath of Schwann.  Schwannoma is a neurogenic tumor usually arising between the third and sixth decades of life, with an equal predilection for men and women. It may occur in any organ or the nerve trunk with the exception of cranial nerves I and II, which lack the Schwann cells.  A retroperitoneal location (retroperitoneal schwannomas) accounts for 0.3-3.2% of all primary schwannomas and 0.3-6.0% of all retroperitoneal tumors.  Schwannomas are usually benign, but infrequently undergo malignant transformation.  Schwannomas usually occur as solitary encapsulated tumors with demarcated margins, with the neighboring organs.  The clinical features are nonspecific and depend on the site of location in the retroperitoneum. A correct preoperative diagnosis is difficult to make and these tumors are often misdiagnosed as other soft-tissue lesions occurring in the retroperitoneum.  We report the case of a 47-year-old female with a benign retroperitoneal schwannoma as a rare one.
| Case Report|| |
A 47-year-old female patient presented with intermittent abdominal pain in her lower abdomen, back pain, and a vague abdominal lump of 10-years.The abdominal pain was independent of activities; it was dull in nature and did not radiate or refer to any other part of the body. There was no history of nausea, vomiting, loss of appetite or weight loss, or any urinary problems. History of constipation and altered bowel habits was present. Systemic examination was within the normal limits. On abdominal examination, a firm, immobile, nontender globular lump was noticed in the hypogastric area. Routine investigations were within the normal limits.Ultrasonography (USG) showed a 10-cm echogenic mass in the retroperitoneal space.Contrast-enhanced computed tomography (CECT) of the abdomen showed a heterogeneous solid mass of about 9 × 6 × 4 cm in the retroperitoneal space, abutting the bifurcation of the aorta [Figure 1] and [Figure 2]. A provisional diagnosis of the retroperitoneal sarcoma was done and surgical exploration was planned. Preliminary examination after laparotomy showed the tumor to be relatively free from surrounding structures; meticulous dissections were done on the common iliac vessels and surrounding structures [Figure 3], and all the feeding vessels were ligated and the tumor was removed.The postoperative course was uneventful. On gross examination, the tumor size was found to be 8 ×6 × 4 cm, with a capsule-like formation [Figure 4]; the cut surface showed a solid smooth grayish white color, with some areas showing cystic changes; no areas of hemorrhage or necrosis was observed [Figure 5]. Histopathological examination showed interlacing bundles and fascicles of the spindle cells having wavy buckled nuclei with prominent Antoni A and Antoni B areas [Figure 6], confirming a schwannoma. The mitotic figures were inconspicuous.
|Figure 2: CECT of the abdomen showing heterogeneous solid mass in the retroperitoneal space, abutting from the bifurcation of the aorta|
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|Figure 6: Histopathological slide showing microscopic feature of the schwannoma|
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| Discussion|| |
The retroperitoneal region is a rare location for schwannomas, except in patients having von Recklinghausen disease. It is also noteworthy to mention that malignant degeneration particularly takes place in association with von Recklinghausen disease.  In 5-18% of patients, there is an association with von Recklinghausen disease; in most cases, these schwannomas are malignant and tend to be present in multiple forms.  Most patients are diagnosed at the age of 25-55 years, but schwannomas can occur at any age. There is no gender predilection. 
In a series of 82 cases, Li et al.  reported retroperitoneal schwannoma between the ages of 6 months and 70 years. The interval between clinical manifestation and diagnosis ranged from 10 days to 2 years. The main symptoms were abdominal distension (30.5%) and abdominal pain (20.7%); 14.4% of patients were accidentally diagnosed and the others had nonspecific symptoms like backache.  In general, since the retroperitoneal space is rather large and flexible, the diagnosis of retroperitoneal schwannoma is often delayed and thus, the lesion reaches a significant size at the time of diagnosis. The most common symptoms are abdominal pain and distension. 
A preoperative diagnosis is very difficult to make due to the lack of typical imaging features [e.g., USG, computed tomography (CT), and magnetic resonance imaging (MRI)] that distinguish schwannomas from retroperitoneal malignancies.  Due to the presence of many anatomical structures in the retroperitoneum, retroperitoneal schwannomas are easily misdiagnosed as psoas abscesses; pancreatic cysts; or adnexal, renal, or adrenal masses. ,,,,
Other diagnoses such as paraganglioma, neurofibroma, ganglioneuroma, tumors of mesodermal origin, and retroperitoneal malignancies including malignant fibrous histiocytoma, lymphoma, and liposarcoma should be considered. 
On MRI, primary retroperitoneal schwannomas show different signal intensity characteristics, including cystic degeneration. There are, however, no specific characteristics of these tumors. 
There are conflicting reports regarding the use of percutaneous USG-or CT-guided biopsies; while some authors recommend them, others object.
Goh et al.  state that sometimes, a CT-guided biopsy may be helpful in the determination. But they do not recommend this modality due to the risks of percutaneous biopsy is hemorrhage, infection, and tumor seeding.
Daneshmand et al.  state that CT-guided fine-needle aspiration biopsy does not appear to provide an accurate preoperative diagnosis.
In a latest series of 28 cases, Strauss et al.  state that cross-sectional imaging combined with a needle biopsy should in all cases provide the correct diagnosis, although they had preoperative diagnosis in only 67.8% of the cases.
With the preoperative assessment of USG-guided fine-needle aspiration, CT, and MRI, the accuracy of diagnosis could definitely be improved and it could later help in the proper planning of excision of the tumor.
Surgical excision is considered the treatment of choice for these tumors. ,, Schwannoma responds poorly to radiation and chemotherapy. ,
The management options include radiologic surveillance in asymptomatic patients who are diagnosed by cross-sectional imaging combined with a needle biopsy. 
Kudo et al.  diagnosed three asymptomatic schwannoma using endoscopic USG-guided fine-needle aspiration biopsy (EUS-FNAB) and followed up the patients without the need of surgical intervention.
There is report of laparoscopic-and robot-assisted resection of the retroperitoneal schwannoma. ,
The goal of surgical excision should be complete excision as it is not possible to have a preoperative diagnosis; histopathological examination of the excised specimen is only diagnostic in most of the cases. Recurrences have been reported with malignant retroperitoneal schwannoma. ,
Subtotal resection had been done with preoperative diagnosis of the benign retroperitoneal schwannoma and on close follow-up, recurrence was not seen. 
Complete resection of the retroperitoneal schwannoma is challenging due to the presence of adjacent or circumscribing major vessels (that is, the aorta and its branches, the inferior vena cava, and others). 
In our case, the tumor had to be resected from the bifurcation of the aorta and the iliac vessels.
Regarding gross appearance, schwannomas are usually solitary, well-circumscribed, firm, and smooth-surfaced tumors. Because of the larger size of the extracranial schwannomas, these are likely to manifest secondary to degenerative changes like cysts and calcifications. 
On histological examination, two main microscopic patterns could be recognized: A highly cellular component (Antoni A area) and a myxoid component (Antoni B area). The predominance of one or the other reflects the heterogeneous findings at radiological investigation (CT and MRI). Almost all the schwannomas showed intense immunohistochemical staining for S100 protein, confirming the neuroectodermal origin of the tumor cell. 
In our case, we established the diagnosis of retroperitoneal schwannoma after histopathological report of the excised specimen.
| Conclusion|| |
To conclude, preoperative diagnosis of retroperitoneal schwannoma is challenging; meticulous dissection is essential for complete excision of the tumor and histopathological examination of the excised tumor is diagnostic for rare retroperitoneal schwannoma as preoperative diagnosis is not possible all the time.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]