CASE REPORT


https://doi.org/10.5005/jp-journals-10033-1608
World Journal of Laparoscopic Surgery
Volume 17 | Issue 1 | Year 2024

Abnormally Located Benign Nerve Sheath Tumor—Retroperitoneal Schwannoma Managed Laparoscopically: A Case Report


B Ramesh1, Priyanka Sukumar2, Kiran R Konda3, Meghana Sreenivas4

1Chief Gynaecological Laparoscopic Surgeon, Altius Hospitals, Bengaluru, Karnataka, India

2–4Department of Minimal Invasive Surgery Gynaecology, Altius Hospitals, Bengaluru, Karnataka, India

Corresponding Author: Kiran R Konda, Department of Minimal Invasive Surgery Gynaecology, Altius Hospitals, Bengaluru, Karnataka, India, Phone: +91 9480507043, e-mail: kiran.rkonda@gmail.com

How to cite this article: Ramesh B, Sukumar P, Konda KR, et al. Abnormally Located Benign Nerve Sheath Tumor—Retroperitoneal Schwannoma Managed Laparoscopically: A Case Report. World J Lap Surg 2024;17(1):61–64.

Source of support: Nil

Conflict of interest: None

Patient consent statement: The author(s) have obtained written informed consent from the patient for publication of the case report details and related images.

Received on: 23 November 2023; Accepted on: 19 December 2023; Published on: 14 February 2024

ABSTRACT

Aim and background: To demonstrate the clinical findings and management of a retroperitoneal Schwannoma, which presented as a gynecological mass. Nerve sheath tumors are benign tumors affecting the cranial and peripheral nerves. Schwannoma refers to tumors arising from the Schwann cells of neurons.

Case description: A 56-year-old female presented to us with vague lower abdominal pain since 3 months. It was initially diagnosed as a inclusion cyst. Intraoperatively diagnosed with retroperitoneal benign looking mass, which turned out to be a schwannoma. We present a case of left-sided retroperitoneal schwannoma which masqueraded as a gynecological mass and operated by laparoscopy.

Conclusion: Schwannomas are benign, encapsulated, slow-growing nerve sheath tumors. Rarely seen in the pelvis and retroperitoneum. Laparoscopy aids in better visualization with more accurate surgical removal of these masses and can be considered the treatment of choice for these tumors.

Clinical significance Often asymptomatic and may go unnoticed, but when presenting with symptoms or when discovered incidentally on scans for other reasons, they are mistaken for gynecological or urological masses and are more often presented to gynecologist/urologist.

Keywords: Case report, Laparoscopy, Nerve sheath tumors, Retroperitoneal, Schwannoma.

INTRODUCTION

Nerve sheath tumors are benign tumor affecting the cranial and peripheral nerves, schwannoma refers to tumors arising from the Schwann cells of neurons. Presence of these tumors are often seen in association with Von Recklinghausen’s disease/Neurofibromatosis. Their occurrence in abdominal/retroperitoneal nerve is seldom seen, with only a few case reports worldwide.1 Mostly asymptomatic, but when presenting with pain or bowel/bladder pressure symptoms, they are often misdiagnosed to be of gynecological or urological origin.2,3 Due to a benign nature with rare local infiltration, a simple excision by laparoscopy suffices for complete management of these cases.4,5

CASE DESCRIPTION

A woman aged 56 years, came to us complaining of vague lower abdominal pain since 3 months, it was not associated with any other symptoms. She had history of loss of appetite since few days, not associated with any weight loss or aggravated pain. Patient was on regular treatment for diabetes mellitus and asthma. No history of any familial cancers or tumors. She had a history of multiple abdominal surgeries in the past—appendicectomy, abdominal hysterectomy with bilateral salpingo-oophorectomy, and cholecystectomy. The patient had also undergone diagnostic laparoscopy with adhesiolysis and stenting of ureters, 2 years prior for abdominal pain not relieving with medication where, no growth or mass was detected intra-abdominally except for omental adhesions. On examination, mild-left lower abdominal tenderness was present with distension. Per speculum examination and per vaginum were unremarkable. Ultrasonography revealed a pelvic cystic mass. She was then advised a contrast-enhanced computed tomography which showed a left adnexal 10 × 4 cm sized well-defined homogenously hypoechoic cystic space occupying lesion which was suggestive of inflammatory/infective etiology (Fig. 1). In view of a cystic mass in the pelvis, all the relevant ovarian tumor markers were checked, which included cancer antigen-125 (CA-125), carcinoembryonic antigen (CEA), cancer antigen (CA 19-9), lactate dehydrogenase (LDH), inhibin, beta-human chorionic gonadotropin (β-HCG) and were found to be normal. With a history of bilateral oophorectomy and a differential diagnosis of peritoneal inclusion cyst, patient was counselled for laparoscopic exploration and excision of mass.

Fig. 1: Axial and sagittal sections of the contrast-enhanced computed tomography showing the mass in the left side of pelvis

Intraoperatively, adhesions involved omentum to anterior abdominal wall near cholecystectomy site, to left lateral pelvic wall, and to uterosacrals. After adhesiolysis, a left retroperitoneal mass was identified after dissecting omental adhesions and left ureterolysis. It was present in front of the sacral promontory, with a smooth surface and a cystic consistency, and no signs of local invasion. All feeding vessels were cauterized and cut. The mass was excised with special care to avoid essential pelvic nerves and vessels. Uterus and adnexa were absent. The specimen was retrieved in bag to avoid spillage into upper abdomen and port site (Fig. 2). Cut section of the mass was homogenous grayish white with 3 mm thickness of the cyst wall.

Figs 2A to F: Laparoscopic excision of the mass. (A) Initial visualization of a retroperitoneal swelling; (B) Close relation of ureter (Yellow arrows) on peritoneal dissection; (C) Excision of mass after adequate ureterolysis; (D) Devascularization of the mass with ultrasonic and bipolar energy (vascular connections-yellow arrow); (E) Mass visualized after complete excision; (F) Mass retrieved in bag through left lower port

Histopathology revealed fibrocollagenous tissue and fibroadipose tissue with tumor composed of cells diffuse sheets and fascicles of bland appearing spindle cells having elongated nucleus with moderate amount of eosinophilic cytoplasm. Stroma showed a myxoid and cystic change. The spindle cells were seen to be entrapping the lobules of mature adipose tissue at periphery. Few ganglion-like cells were seen. Mitotic activity was 0–2 per high power field and margins were free of tumor. This low-grade spindle cell neoplasm was reactive with S100 and SOX10 (SRY-Box Transcription Factor 10) and patchy reactivity with CD34 (Cluster of Differentiation 34). About 5% of the tumor cells had Ki67 (Antigen Kiel 67) reactivity and negative for epithelial membrane antigen (EMA) and smooth muscle actin (SMA) on immunohistochemistry (IHC), thus diagnosing nerve sheath tumor (Fig. 3).

Figs 3A to C: (A) Fibrocollagenous tissue and fibroadipose tissue with a tumor composed of cells diffuse sheets and fascicles of bland appearing spindle cells having elongated nucleus with moderate amount of eosinophilic cytoplasm; (B) S100 positivity on IHC; (C) SOX10 positivity on IHC

Postoperatively the patient recovery was uneventful and was discharged at 48 hours. Patient had complete relief from pain on 1-month and 6-month follow-up with no signs of recurrence of mass on ultrasonography.

DISCUSSION

Schwannomas, neurofibroma, solitary circumscribed neuroma, and perineuriomas are soft tissue tumors of the nerve sheath.2 Benign peripheral nerve sheath tumors can occur sporadically or as manifestations of genetic syndromes, such as neurofibromatosis types 1/Von Recklinghausen’s disease and neurofibromatosis 2. Schwannomas arise from the Schwann cells covering the neurons, most seen in peripheral and cranial nerve trunks (except cranial nerve 1 and 2) and rarely seen in retroperitoneal nerves (0.3–3.2%). They are mostly solitary tumors, well circumscribed with no local tissue invasion and multiple lesions only seen in association with neurofibromatosis 1.2,4

Due to a slow growing and asymptomatic nature, patients rarely present for this condition, they are often discovered incidentally during investigation for other problems.2 As seen in our patient, when symptomatic, they may present with chronic pelvic pain or pressure symptoms over bowel/bladder.3,6 Local recurrence is prevented by complete resection and rarely transform to malignant mass.7 They have been reported to be arising from pelvic nerves and retroperitoneal tissue with the involvement of broad ligaments and pressure symptoms.1

Ultrasonography as the first-line investigation is best for detecting cystic lesions. Therefore, computed tomography and magnetic resonance Imaging may be useful for distinguishing these masses. Although, the features of most retroperitoneal tumors are still non-specific.8 As was seen in our case, a cystic mass was reported in the left adnexa on contrast-enhanced computed tomography, which intraoperatively turned out to be a retroperitoneal mass. Imaging-guided core needle biopsy by radiologists provides correct diagnosis.2 However, Daneshmand S et al. reported that preoperative diagnosis of Schwannomas with computed tomography-guided fine needle aspiration biopsy fails to provide accurate diagnosis.4

Histologically, encapsulated mass displays alternating areas of dense cellularity and areas of myxoid matrix (Antoni-A and Antoni-B regions). Antoni-A regions have dense aggregation of spindle-shaped cells arranged in parallel configurations, palisades, or whorls. Antoni-B regions show hypocellularity with predominantly loose myxoid matrix. Immunohistochemistry is positive for S-100, Vimentin, and neuron-specific enolase. Smooth muscle actin and CD117 are negative. Ancient Schwannoma, a variant characterized by degenerative features, such as cystic necrosis, stromal edema, fibrosis, perivascular hyalinization, calcification, and degenerative nuclei with pleomorphism, lobulation, and hyperchromasia.9 S100 and SOX10 IHC markers which are more specific markers for Schwannomas and CD34 positivity usually seen in Antoni-A areas. Ki67 index is a marker for high replication rate and malignancy. Epithelial membrane antigen normally expressed in perineurial cells; therefore, it is positive stained in perineuriomas and malignant peripheral nerve sheath tumor (MPNST) with perineurial differentiation, but negative in schwannomas.10 The IHC markers in our case were conclusive of a benign schwannoma.

Complete resection is the best treatment for schwannomas.11 Research indicates an increased risk of neurologic deficit after complete excision with adjacent tissue. However, malignant transformation and local recurrence are very rare after complete resection.5 Laparoscopy is safe and efficient option for approaching these schwannomas and it offers the advantage of better visualization of structures with magnification, especially in narrow anatomic spaces.12 As seen in the present case report, laparoscopy allowed for better visualization of abdomen, with detailed pelvic anatomy and aided in fine dissection of the left ureter which was in close relation to the mass.

CONCLUSION

Schwannomas are benign, encapsulated, slow-growing nerve sheath tumors. They are rarely seen in the pelvis and retroperitoneum. They are often asymptomatic and may go unnoticed, but when presenting with symptoms or when discovered incidentally on scans for other reasons, they are mistaken for gynecological or urological masses and are more often presented to gynecologist/urologist. Malignancy is very rare and often surgical excision of mass suffice and prevent further growth or recurrence. Laparoscopy aids in better visualization with more accurate surgical removal of these masses and can be considered the treatment of choice for these tumors.

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