RETROPERITONEAL SCHWANNOMA

RETROPERITONEAL SCHWANNOMA

ARSHAD S KHAN*, GIRISH D BAKHSHI*, PRASHANT B SANKAYE*,HEMANT G BORSE*, NEETA D SHAH*, GRACE F D’COSTA+
*Department of Surgery, +Department of Pathology, Grant Medical College and JJ Group of Hospitals, Mumbai - 400 008.

The retroperitoneal localization of a schwannoma or neurilemmoma represents an unusual occurrence (0.5-1.2% of all sites);[1] this data, together with the absence of a typical clinical picture and the lack of peculiar instrument signs, make a preoperative diagnosis of this lesion really hard to ascertain. We present a case of 30 year old female who presented with painless retroperitoneal lump. Investigations preoperatively could not confirm the diagnosis. Patient was operated through a retroperitoneal approach and the diagnosis of retroperitoneal schwannoma was confirmed by histological study of the resected specimen. Post-operative follow up of one year has shown her to be disease free clinically and radiologically.

INTRODUCTION

Schwannomas are well-encapsulated tumours arising from the peripheral nerve sheath, usually in young and middle-aged adults. They are seen commonly in the soft tissues of the head, neck, extremities and mediastinum. The retroperitoneum is rarely involved.[2] This tumour is clinically unspecified and in most of the cases it originates symptoms coming from the compression of the close structures when its localization is retroperitoneal. With a varied presentation and a difficult preoperative diagnosis, schwannoma accounts for only a small percentage of retroperitoneal tumours. Its diagnosis is quite often being confirmed by anatomopathological study afterwards.[3] We report a case of this uncommon retroperitoneal pathology in a female patient. One year after the surgery she remains asymptomatic without any radiological evidence of recurrence.

CASE REPORT

A 30 year old woman presented with lump in the right side of the abdomen since 4 months. She had no history of fever, weight loss or anorexia. On abdominal examination, a large retroperitoneal lump measuring 10 cm x 10 cm was found in the right hypochondriac region extending into the right lumbar region with a smooth surface, firm in consistency and nonpulsatile. Examination of other systems and laboratory parameters were within normal limits.

Ultrasonography (USG) showed a well-defined echogenic mass in the right retroperitoneal region pushing the right kidney anteriorly and medially. Non-contrast computed tomography (CT) showed a sharply demarcated hypodense mass. On contrast enhanced CT, there was a thick rim of enhancement in the periphery of the lesion with central hypodensity. It was located just lateral and posterior to the right kidney below the right lobe of liver. Patient was worked up for surgery. A retroperitoneal approach was taken which showed a well-encapsulated retroperitoneal tumour lateral and posterior to the right kidney. The resected specimen demonstrated a firm and well demarcated capsulated tumour measuring 10 cm x 10 cm in size, pale yellow in colour with a heterogeneous consistency at the cut surface of the gross section.

Histopathologic examination revealed areas of Antoni type A (cellular pattern) and Antoni type B (sparse cellular pattern with cystic degeneration and xanthomatous changes) cells, (Fig. 1), which confirmed the diagnosis of retroperitoneal schwannoma. Post-operative period was uneventful. Post-operative follow up of one year has shown patient to be disease free clinically and on USG.

Fig. 1: Neurilemmoma showing compact spindle cells (Antoni A areas) admixed with loose textured areas showing small round cells (Antoni B areas) haematoxylin and eosin stains (20X).

DISCUSSION

Schwannoma, a relatively rare retroperitoneal tumour, has a reported incidence of only 0.5-1.2%,[1] which may make an accurate preoperative diagnosis difficult.[4] However, it is clinically essential to determine whether the tumour really exists in the retroperitoneum before analyzing it on a qualitative basis. Determination of tumour location must be done with great care when the mass exists between the liver and the retroperitoneum, and especially when the tumour is hypovascular. The lesions learned from this case may be of value for the correct diagnosis of tumours located deep in the abdomen, or between the abdominal organs.

The low frequency of this tumour and the lack of specific instrumental signs and objective symptoms (since it develops in a deep and broad region as retroperitoneum) make presurgical diagnosis very difficult.[4] Clinically, early detection of the tumour is difficult unless it enlarges and becomes palpable or compresses the surrounding organs.[3]

Abdominal USG is a simple and non-invasive method used for early detection. Small masses are usually solid and hypoechoic. As the tumour grows, areas of necrosis and cystic degeneration appear.[5] On CT, schwannomas appear as well-demarcated, hypodense, homogeneous masses. After contrast administration they appear heterogeneous with ring enhancement.[2] Well-defined round masses with multiple well-demarcated cystic necrotic areas have been reported in previous studies.[5] The information provided by ultrasonography, CT and magnetic resonance imaging help to limit diagnostic hypothesis, but they do not show any pathognomonic images. It can be confirmed only during surgery and definitive histological examination.[3,6] The resection of this tumour is the appropriate treatment, even though it is really a complex one. Prognosis is quite good since post-surgical recurrences are unusual.[6] Hence to summarise, a retropertoneal schwannoma is a tumour with multiple presentation and difficult preoperative diagnosis, it is important to recognize these tumours as benign with excellent prognosis so as to avoid unnecessary radical surgery.

ACKNOWLEDGEMENT

We would like to thank Dean and Dr. GB Daver Head of the Department of Surgery, Grant Medical College and JJ Group of Hospitals for granting us permission to publish this case report.

REFERENCES

1.Maeshima S, Nakamura H, Nishikawa M, Murakami T, Mitani T, Murukawa T, et al. Retroperitoneal schwannomas simulating adrenal tumours. Clin Imaging 1992; 16 : 121-4.

2.Sewng Hyup Kim, Byung Ihn Choi. Retroperitoneal neurilemmoma: CT and MR findings. AJR 1992; 159 : 1023-6.
3.De Diego Rodriguez E, Roca Edreira A, Martin Garcia B, et al. Retroperitoneal benign schwannoma. Report of a new case. Actas Urol Esp 2000; 24 (8) : 685-8.

4.Perhoniemi V, Anttinen I, Kadri F, Saario I. Benign retroperitoneal schwannoma. Scand J Urol Nephrol 1992; 26 : 85-7.

5.Chung-Huang Kuo, Chi-Sin Changchien. Sonographic features of retroperitoneal neurilemmoma. J Clin Ultrasound 1993; 21 : 309-12.

6.Ben Moualli S, Hajri M, Ben Amna M, et al. Retroperitoneal schwannoma. Case Report Ann Urol (Paris) 2001; 35 (5) : 270-2.

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Fig. 1: Neurilemmoma showing compact spindle cells (Antoni A areas) admixed with loose textured areas showing small round cells (Antoni B areas) haematoxylin and eosin stains (20X).