Two giant connected retroperitoneal schwannomas: a rare case report

Abstract

Schwannoma is a type of tumor originating from Schwann cells of peripheral nerves. In this study, we report a rare case of two giant connected retroperitoneal schwannomas. The patient presented to our department with a 1-day history of abdominal pain and without other symptoms. There were no abnormalities in the patient’s tumor markers. Abdominal plain computed tomography (CT) revealed two (combined) retroperitoneal masses appearing as soft tissue-density shadows with uneven internal density, cystic low-density shadows, and patchy calcification shadows. The larger mass measured approximately 12.0 cm × 12.3 cm in size. The tumors were completely excised by a reasonable surgical approach while the surrounding organs closely related to the tumor were preserved. Postoperative pathology confirmed that the tumors were benign schwannomas. In the 18-month follow-up, the patient had no recurrences and was asymptomatic. We summarize the diagnosis and treatment of two rare combined giant retroperitoneal schwannomas in a single patient. Laparotomy for the management of retroperitoneal giant schwannomas may be safe and effective.

Introduction

Schwannoma is a type of tumor originating from Schwann cells of peripheral nerves. Schwannoma is the most common peripheral nerve tumor and is usually benign;^1,2 some tumors have neuroendocrine functions. ³ Schwannomas usually occur in patients aged 20 to 50 years of age, with no significant sex difference. ⁴ They are common in the head, neck and limbs, ⁵ and can also occur in the larynx, liver, mediastinum, and retroperitoneal space. ⁴ Retroperitoneal schwannomas account for 0.3% to 3.0% of all schwannomas,^2,6 and schwannomas account for 1% of all retroperitoneal tumors. ⁷ Herein, we report a case of two giant connected retroperitoneal schwannomas in a single patient, which received satisfactory treatment results by complete resection of the tumors and preservation of the surrounding organs.

We have obtained the patient’s written informed consent for treatment and have withheld any information that would identify the patient, in this report. The reporting of this study conforms to the CARE guidelines. ⁸ This study was approved by the review board of our hospital for publication.

Case report

A woman in her early 40 s (body mass index: 21.9 kg/m²) presented to our department with a 1-day history of abdominal pain. A mass was found in her left abdomen 2 months previously, and no systematic diagnosis and treatment was performed at that time. The patient came to our department because of abdominal pain, with no other specific symptoms. She had a history of hepatitis-related jaundice that had been cured. She had no history of surgery or hypertension and had a normal menstrual history. Her father and an uncle had died of stomach cancer. On physical examination, left abdominal swelling was observed, and palpation revealed a hard and fixed mass. Laboratory testing revealed the following abnormalities: hemoglobin: 80 g/L and C-reactive protein concentration: 74.5 mg/L (0.0745 g/L). Tumor markers (carcinoembryonic antigen (CEA), carbohydrate antigen 199 (CA199), and alphafetoprotein (AFP)) were measured, and no concentrations were abnormal. Abdominal plain computed tomography (CT) revealed two retroperitoneal soft tissue density mass shadows, with uneven internal density, cystic low-density shadows, and patchy calcification shadows.

The larger mass measured approximately 8 cm × 8 cm in size, with a CT value of 14 to 45 HU, clear boundaries, and displacement of adjacent organs owing to compression. No enlarged retroperitoneal lymph nodes were observed. Contrast-enhanced CT (Figure 1a) after admission showed that the lesions had an obvious space-occupying effect, and the upper part of the lesions was indistinct from the psoas major muscle. In the arterial phase, multiple arterial vessels supplying blood from the abdominal aorta were seen, with no enhancement in the venous phase. Multiple cystic low-density shadows were seen in the lesions, and the enhancement degree was weaker in the shadows than that in the lesions’ parenchyma. Three-dimensional CT reconstruction (Figure 1b, c) of the tumors revealed displacement of the abdominal aorta and left kidney owing to compression, with renal arteries and veins spanning the surface of the tumors. On the basis of the initial findings and the imaging findings with enhanced CT, the possibility of sarcoma was considered. Considering the possibility of performing combined left nephrectomy with tumor resection, we performed CT urography before surgery, and the findings suggested that both kidneys had good blood perfusion, normal function, and unobstructed excretion. After the preoperative discussion, we decided to remove the tumors using an approach through the left paracolic sulcus into the retroperitoneal space.

Figure 1.

Contrast-enhanced CT and three-dimensional CT reconstruction of the tumors. (a) Contrast-enhanced CT showing that the combined tumors are located on the left side of the spine, behind the left renal arteries and veins, ureters, and spleen. (b) Three-dimensional CT reconstruction showing that the medial edge of the tumors is attached to the left side of the abdominal aorta and (c) The tumors compress the abdominal aorta to the right, and the left renal artery and vein span the tumor surface.

CT, computed tomography.

Surgery was performed with the patient under general anesthesia in the supine position. An incision in the left rectus abdominis was made to enter the abdominal cavity, with dissection proceeding in layers. The abdominal cavity was examined, and no obvious adhesions or effusion were observed. The surfaces of the liver and spleen were smooth, and no masses were seen in these organs. Additionally, no masses were seen in the stomach, small intestine, omentum, ileocecum, colon, or upper rectum. No abnormalities were found in bilateral appendages or in the uterus. The two retroperitoneal tumors were large and had abundant blood vessels on their surfaces (Figure 2a). The surface of the combined tumors was covered by the greater omentum and left mesentery, and the tumors were located on the left side of the spine, behind the left renal arteries and veins, ureters, tail of the pancreas, and spleen. The upper end of the tumors reached the left diaphragm, and the lower end reached the iliac fossa. The medial edge of the tumors was attached to the left side of the abdominal aorta, and the lateral edge reached the left paracolic sulcus.

Figure 2.

Pathological features of the tumor and abdominal CT post-surgery. (a) After opening the abdominal cavity, abundant blood vessels can be seen on the tumor surface and (b) The postoperative specimen sizes for each mass were 8.0 cm × 7.0 cm × 5.5 cm and 4.0 cm × 5.0 cm × 6.0 cm, respectively.

CT, computed tomography.

The specific surgical procedures were as follows: First, the paracolic peritoneum was incised from the left paracolic sulcus, and the incision was extended upward and downward to dissociate and release the left kidney, tail of the pancreas, and the spleen. Care was taken to protect the blood vessels of the spleen and kidney, and the ureters. Then, the loosened spleen and left kidney were pushed to the midline of the abdominal cavity to fully expose the left retroperitoneal space, and the tumors were confirmed as two masses. Careful dissection along the capsules of the tumors and en bloc excision were performed. Ligation for hemostasis was performed at the bleeding point of the surgical bed. Finally, we confirmed that there was no damage to the left colon, kidneys, tail of the pancreas, and spleen. After lavaging the abdominal cavity with warm saline, a closed drain was placed in the surgical bed; the drain was retained for 10 days. The surgical duration was 180 minutes, and there were no intraoperative complications. The intraoperative blood loss volume was approximately 200 mL. Examination of the surgical specimens (Figure 2b) revealed two pale, yellow, enveloped tumors, with smooth surfaces and hard textures. The larger mass measured 8.0 cm × 7.0 cm ×5.5 cm, and the smaller mass measured 4.0 cm × 5.0 cm ×6.0 cm; both masses underwent pathological examination. Histological results showed that the tumor parenchymas were composed of Schwann cells with light to moderate nuclear atypia (Figure 3). Immunohistochemical staining revealed the following: S-100 (+), SOX10 (+), desmin (−), cluster of differentiation 34 (CD34) (vessel+), smooth muscle actin (SMA) (−), Bcl-2 (−), Ki67 positivity rate: 1%, estrogen receptor (ER) (−), progesterone reception (PR) (−), nuclear factor kappa B (NF-kB) (−), and CD99 (−) (Figure 4). The histological findings and immunohistochemistry results confirmed the tumors as benign schwannomas. The patient was discharged from our hospital on the 10th postoperative day; the duration of the hospital stay was 15 days. CT 18 months after the operation showed no signs of tumor recurrence (Figure 5).

Figure 3.

Histopathology showing that the tumor parenchyma is composed of Schwann cells with light to moderate nuclear atypia (hematoxylin–eosin staining; magnification, ×200).

Figure 4.

Immunohistopathology showing the following: S-100 (+), SOX10 (+), and Ki67 positivity rate: 1% (magnification, ×200)

Figure 5.

CT image 18 months after surgery showing no signs of recurrence

CT, computed tomography.

Discussion

Retroperitoneal schwannomas are generally solitary masses with well-defined and intact envelopes, ¹ most of which are located near the great vessels.^2,5 These tumors may be solid or multilocular cystic with hemorrhage and necrosis. ⁹ Microscopically, the tumor is composed of two distinct regions of Schwann cells. ⁹ One region is the cell-rich Antoni A region, in which the cells are fusiform or oval in shape and arranged into tactile corpuscles or eosinophil corpuscles. The other region is the sparsely cellular Antoni B region, in which the cells are loosely arranged in a mucoid matrix, and pathological variations appear as epithelioid or calcified. ⁴ The typical immunohistochemical features of schwannomas are S100 protein- and SOX10-positive but desmin-negative.^2,10–12 In our case, the expression of S100 protein and SOX10 in the tumor cells was positive, while desmin expression was negative, which was consistent with the immunohistochemical characteristics of schwannoma. The positivity rate of Ki67 in the tumor cells was only 1%, indicating a low degree of malignancy.

Studies have shown that the occurrence of schwannomas is mainly related to the deletion of tumor suppressor protein merlin. ¹³ The NF2 gene encodes the tumor suppressor protein merlin. ¹³ There is no evidence in the current literature linking NF genes to gastric cancer. This patient had a family history of gastric cancer; however, there is no evidence in the current literature to support an association between the occurrence of retroperitoneal schwannoma and gastric cancer. Schwannomas that occur in the stomach are generally benign tumors. ¹⁴ Although there are individual case reports of concurrent gastric adenocarcinoma and gastric schwannoma, this event is rare,^15,16 and the extremely low incidence does not support a relationship between these tumors.

Small nonfunctional retroperitoneal schwannomas are often asymptomatic. ¹⁷ However, as these tumors grow, patients may develop abdominal pain, abdominal distension, constipation, and other symptoms, although there is no specificity in these signs. ¹⁸ Multiple retroperitoneal schwannomas are extremely rare. Bai et al. ¹⁷ reported a case of retroperitoneal primary multiple obturator schwannomas with only mild abdominal pain. A good therapeutic effect was achieved after surgical resection. ¹⁷ In previous reports, multiple schwannomas were more likely to appear in the distribution area of the craniofacial nerves, and the clinical symptoms were related to the location of the tumors; for example, pain, lumps, and symptoms related to pressure on other organs.^18,19 Currently, a preoperative diagnosis of schwannoma relies mainly on CT and magnetic resonance imaging (MRI); however, the imaging findings are nonspecific. In our case, the preoperative CT findings of schwannoma indicated that the tumors’ boundaries were clear, the density inside the tumors was uneven, and cystic changes and calcification shadows were visible. However, there were no enlarged retroperitoneal lymph nodes.

Contrast-enhanced CT showed heterogeneous enhancement within the tumors, and vascular shadows were seen at the edges of the lesions in the arterial phase. These findings are consistent with the histological structure and imaging features of schwannoma. MRI can show the blood supply of a tumor more clearly, which indicates its enhancement characteristics. ⁴ Most schwannomas appear as low intensity on T1-weighted images and heterogeneous high intensity on T2-weighted images. ⁴ Our previous work showed that the combination of CT and MRI can improve the diagnostic accuracy of retroperitoneal schwannomas. Currently, positron emission tomography (PET)/CT is gradually be used more often in the diagnosis of schwannoma, and PET/CT may be useful in differentiating benign from malignant tumors. ²⁰ Although Theodosopoulos et al.^5,21 believe that puncture biopsy is helpful for a preoperative diagnosis of schwannoma, this method may lead to a misdiagnosis owing to the heterogeneity of these tumors. Furthermore, puncture biopsy may lead to the spread of tumor cells. Therefore, Maccio et al. ² do not recommend preoperative puncture biopsy. However, Sultan et al. ³ suggested that nonfunctional and well-encapsulated heterogeneous retroperitoneal schwannomas could be biopsied.

To the best of our knowledge, because only a few cases of large retroperitoneal schwannomas have been reported in the literature, guidelines on the optimal surgical treatment are lacking. In accordance with the research of Ogose et al., ²² the average growth rate of retroperitoneal schwannomas is 1.9 mm/year (range: 1.9–8.7 mm/year). Therefore, most asymptomatic patients may be suitable for management with a “wait and see” approach. However, Kitagawa et al. ²³ argued that cancer growth patterns cannot be accurately predicted based on a patient’s symptoms and imaging studies. Because of the obvious space-occupying or compression effect of giant retroperitoneal schwannomas, regardless of whether a giant retroperitoneal schwannoma is benign or malignant, active treatment should be pursued. Currently, the ideal surgical procedure for retroperitoneal schwannomas is controversial. First, regarding the resection scope, local recurrence and malignant transformation of retroperitoneal schwannomas are extremely rare. ⁶ As a result, it is suggested that patients with retroperitoneal schwannomas excluded from having Recklinghausen’s disease may be treated with local resection, while preserving adjacent important organs.^6,24 However, prior to a clear diagnosis of schwannoma, it is necessary to appropriately expand the resection boundary or even resect the adjacent organs. Even if a schwannoma is confirmed to be malignant by postoperative pathology, the local recurrence rate can be reduced significantly by extending the resection range.^21,25

Regarding the surgical methods, open operation is still the first choice for large retroperitoneal schwannomas. ²¹ Theodosopoulos et al. ²¹ reported three cases of open resection of retroperitoneal schwannoma, of which two cases were combined with partial resection of the psoas muscle and in one case, with hysterectomy. During the 48-month follow-up, the patients did not develop tumor recurrence, and all remained asymptomatic. There are also reports of laparoscopic or robot-assisted resection of retroperitoneal schwannomas.^2,26–30 However, nine cases of schwannomas near the great vessels have been reported; ² therefore, laparoscopic surgery cannot be considered absolutely safe. In our opinion, we believe that retroperitoneal schwannomas are unsuitable for laparoscopic surgery when the tumors are large and closely related to the surrounding large vessels or organs. Laparoscopic resection may be considered for tumors that are small, isolated, and located away from larger vessels. However, the safety and long-term efficacy of laparoscopic surgery requires further evaluation. In the current case, the patient’s tumors were large; deep and fixed in location; and closely related to the abdominal aorta and renal arteries and veins. To facilitate the exploration and removal of the tumors, a surgical approach via the left paracolic sulcus was performed. Because the tumor capsules were intact, and there was no surrounding invasion, the resection margin was not enlarged. At the 18-month follow-up, the patient had not developed recurrence and was asymptomatic.

In this report, we summarized the diagnosis and treatment of two rare giant combined retroperitoneal schwannomas in a single patient. Preoperative biopsy of these tumors should be considered carefully. The size and location of the tumor are important factors in determining the surgical method and approach. Laparotomy is feasible for larger retroperitoneal schwannomas, and laparoscopic surgery may be considered for smaller tumors.

Availability of data and materials

All data generated or analyzed in this study are included in the published article.

ORCID iDs

Tongjun Liu https://orcid.org/0000-0001-5712-4838

Bo Li https://orcid.org/0000-0002-9789-2513