Case Report Open Access
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World J Gastroenterol. Apr 7, 2012; 18(13): 1538-1544
Published online Apr 7, 2012. doi: 10.3748/wjg.v18.i13.1538
Pancreatic schwannoma: Case report and an updated 30-year review of the literature yielding 47 cases
Toshiyuki Moriya, Wataru Kimura, Ichiro Hirai, Akiko Takeshita, Koji Tezuka, Toshihiro Watanabe, Masaomi Mizutani, Akira Fuse
Toshiyuki Moriya, Wataru Kimura, Ichiro Hirai, Akiko Takeshita, Koji Tezuka, Toshihiro Watanabe, Masaomi Mizutani, Akira Fuse, First Department of Surgery, Yamagata University Faculty of Medicine, 2-2-2 Iida-Nishi, Yamagata 990-9585, Japan
Author contributions: Moriya T, Kimura W, Hirai I, Takeshita A, Tezuka K, Watanabe T, Mizutani M and Fuse A performed surgery and clinical follow-up; Moriya T analyzed data and wrote the paper.
Correspondence to: Wataru Kimura, MD, First Department of Surgery, Yamagata University Faculty of Medicine, 2-2-2 Iida-Nishi, Yamagata 990-9585, Japan. wkimura@med.id.yamagata-u.ac.jp
Telephone: +81-23-6285336 Fax: +81-23-6285339
Received: December 7, 2010
Revised: January 24, 2011
Accepted: January 31, 2011
Published online: April 7, 2012

Abstract

Pancreatic schwannomas are rare neoplasms. Authors briefly describe a 64-year-old female patient with cystic pancreatic schwannoma mimicking other cystic tumors and review the literature. Databases for PubMed were searched for English-language articles from 1980 to 2010 using a list of keywords, as well as references from review articles. Only 41 articles, including 47 cases, have been reported in the English literature. The mean age was 55.7 years (range 20-87 years), with 45% of patients being male. Mean tumor size was 6.2 cm (range 1-20 cm). Tumor location was the head (40%), head and body (6%), body (21%), body and tail (15%), tail (4%), and uncinate process (13%). Thirty-four percent of patients exhibited solid tumors and 60% of patients exhibited cystic tumors. Treatment included pancreaticoduodenectomy (32%), distal pancreatectomy (21%), enucleation (15%), unresectable (4%), refused operation (2%) and the detail of resection was not specified in 26% of patients. No patients died of disease with a mean follow-up of 15.7 mo (range 3-65 mo), although 5 (11%) patients had a malignancy. The tumor size was significantly related to malignant tumor (13.8 ± 6.2 cm for malignancy vs 5.5 ± 4.4 cm for benign, P = 0.001) and cystic formation (7.9 ± 5.9 cm for cystic tumor vs 3.9 ± 2.4 cm for solid tumor, P = 0.005). The preoperative diagnosis of pancreatic schwannoma remains difficult. Cystic pancreatic schwannomas should be considered in the differential diagnosis of cystic neoplasms and pseudocysts. In our case, intraoperative frozen section confirmed the diagnosis of a schwannoma. Simple enucleation may be adequate, if this is possible.

Key Words: Pancreatic schwannoma, Pancreas, Schwannoma, Neurinoma, Resection, Imaging, Enucleation, Prognosis, Cystic



INTRODUCTION

Pancreatic schwannomas are rare neoplasms that originate from Schwann cells. The Schwann cells line the nerve sheath and can generate either schwannoma or neurofibroma[1]. Schwannoma usually occur in the extremities, but can also be found in the trunk, head and neck, retroperitoneum, mediastinum, pelvis and rectum[2,3]. Pancreatic schwannomas are even more unusual neoplasms that affect adults with an equal gender distribution[4,5]. These tumors vary considerably in size and approximately two-thirds are reported to undergo degenerative changes including cyst formation, calcification, hemorrhage, hyalinization and xanthomatous infiltration[4,5]. As a result, they may radiographically mimic cystic pancreatic lesions (e.g., mucinous cystic neoplasms, solid and pseudopapillary neoplasms, serous cystic neoplasms, and pseudocysts).

Only 47 cases have been reported in the English literature in the last three decades[2-42]. In this report, we present a case of pancreatic schwannoma and provide a pertinent review of literature with emphasis on clinical presentation, diagnosis, treatment options, and outcome.

CASE REPORT

A 64-year-old previously healthy woman was incidentally discovered to have a cystic tumor in the pancreas during an ultrasound examination for a health check. She was referred to our institution for further investigation. The abdominal physical examination did not detect any marked finding and all laboratory data were normal, including tumor markers. The computed tomography (CT) scan demonstrated a well-encapsulated tumor, which was composed of solid and cystic areas (Figure 1), and neither liver mass nor peripancreatic lymph node swelling was detected. Magnetic resonance imaging (MRI) showed a mass, with hypointensity on T1-weighted images and hyperintensity on T2-weighted images. Magnetic resonance cholangiopancreatography (MRCP) showed a hyperintense mass in the pancreatic head with no dilatation of the main pancreatic duct. Endoscopic retrograde cholangiopancreatography revealed no communication between cystic tumor and pancreatic duct. Endoscopic ultrasonography showed that the tumor was composed of cystic part and solid part. We performed surgery under the diagnosis of cystic tumor of the pancreas as mucinous cystic tumor, solid pseudo papillary tumor or gastrointestinal stromal tumor. The laparotomy disclosed a well-encapsulated 4-cm mass in the uncinate process of the pancreas that had no signs of inflammation. Intraoperative ultrasound confirmed a solitary mass composed of solid and cystic components (Figure 2). The mass was enucleated and an intraoperative frozen section demonstrated a benign schwannoma. No further resection was performed based on these findings. The tumor was 4 cm × 4 cm × 3 cm in size, and was composed of a mixture of solid and hemorrhage areas. On microscopic examination, the tumor was composed of spindle cells strongly positive for S-100 proteins and foci of hemorrhage (hematoxylin and eosin, × 100) (Figure 3). The tumor cells were negative for smooth muscle actin and CD-34. The tumor was therefore histologically diagnosed as benign schwannoma. The patient was discharged uneventfully on postoperative day 17. At a 65-month follow up after resection, the patient is doing well without any recurrent disease.

Figure 1
Figure 1 Contrast-enhanced computed tomography scan obtained in the arterial phase showing a multilocular cystic mass in the uncinate process of the pancreas. No pancreatic ductal dilatation or invasion into adjacent arteries or portal vein are identified.
Figure 2
Figure 2 Intraoperative ultrasound showing the well-encapsulated pancreatic mass that is composed of solid and cystic components.
Figure 3
Figure 3 Microscopic examination demonstrating spindle cells without nuclear atypism (HE x 100). Immunohistochemical staining for S-100 protein was positive. HE: Hematoxylin and eosin.
DISCUSSION

A review of the patient’s chart was performed along with a review of English-language articles using a PubMed search for the last three decades. We found 41 articles including 47 patients with pancreatic schwannoma. Details of the cases are summarized in Table 1 along with the current patient. Table 2 summarizes the important available facts regarding all patients. We examined the correlation between tumor size and malignancy, as well as tumor size and cystic degeneration. Continuous data are presented as mean ± standard deviation and range. Student t-test was used for all comparisons among continuous variables. A P < 0.05 was considered statistically significant.

Table 1 Summary of cases with pancreatic schwannoma.
AuthorYearSexAgePresenting symptomsSize(cm)LocationSolid/cystic by imageTreatmentHistologyFollow-up (mo)
Current case2010F64Asymptomatic4.0UncinateSolid and cysticEnucleationBenign65
Dorsey et al[6]2010F54Abdominal pain, weight loss1.4HeadSolidNABenignNA
Stojanovic et al[7]2010F24Abdominal pain, dyspepsia, weight loss, palpable tumor18.0Body/tailCysticDP + transverse colonMalignant28
Suzuki et al[8]2010F66Asymptomatic3.0BodySolid and cysticDPBenign24
Aggarwal et al[9]2010M20Upper abdominal discomfort3.0HeadNAEnucleationBenignNA
Ohshima et al[10]2010F32Back pain4.0HeadSolid and cysticPDBenignNA
Mummadi et al[11]2009M35Epigastric pain7.0BodySolid and cysticNABenign6
Gupta et al[5]2009F56Asymptomatic8.3Head/bodyCysticPDBenignNA
Li et al[12]2009M37Asymptomatic16.0HeadSolid and CysticPDBenignNA
Tafe et al[13]2008M46Abdominal pain11.0Body/tailCysticDPBenignNA
Hirabayashi et al[14]2008M51Asymptomatic6.0TailCysticDPBenignNA
Okuma et al[15]2008F71Epigastric pain4.0BodySolid and cysticDPBenignNA
Tofigh et al[16]2008M54Epigastric pain, weight loss, nausea, intermittent jaundice3.0HeadSolid (by specimen)PDBenign
Fasanella et al[17]2007M36Abdominal discomfort3.6UncinateCysticNABenignNA
Di Benedetto et al[18]2007M42Asymptomatic2.5BodySolidDPBenignNA
Yu et al[19]2006M72Upper abdominal pain1.0Head/bodySolidNABenignNA
Wu et al[20]2005M71Epigastric pain, decreased appetite1.5HeadCysticEnucleationBenign10
Novellas et al[21]2005F46Asthenia, weight loss, empyema3.0HeadSolidPDBenign24
Soumaoro et al[22]2005F64Asymptomatic2.5HeadSolidEnucleationBenign24
Bui et al[23]2004F69Abdominal pain5.0HeadSolidUnresectableNA1NA
Akiyoshi et al[24]2004F67Asymptomatic5.0HeadCysticPDBenign43
Von Dobschuetz et al[25]2004F55Asymptomatic8.0HeadCysticPD + PV reconstructionBenign10
Paranjape et al[4]2004F77Upper abdominal pain, weight loss3.5BodySolidEnucleationBenign3
Tan et al[26]2003F46Right upper quadrant pain2.2HeadSolid and CysticPDBenignNA
Almo et al[2]2001F73Abdominal pain, nausea, vomiting3.0HeadCysticPDBenign17
Almo et al[2]2001F47Abdominal pain, back pain5.5HeadSolidPDBenign14
Lee et al[27]2001F63Upper abdominal pain10.0TailCysticDPBenign6
Morita et al[28]1999F50Upper abdominal pain9.5Body/tailCysticDPBenign7
Brown et al[29]1998M52Asymptomatic5.5BodyCysticResection2BenignNA
Brown et al[29]1998M69Asymptomatic6.0HeadCysticPDBenignNA
Hsiano et al[30]1998F70Palpable tumor18.0Body/tailCysticResection2Benign24
Feldman et al[31]1997M63Asymptomatic2.5BodySolidEnucleationBenignNA
Feldman et al[31]1997F54Abdominal pain2.0UncinateSolidEnucleationBenign22
Ferrozzi et al[32]1995M47Right-sided abdominal pain3.5BodyNADPBenign48
Ferrozzi et al[32]1995M63Abdominal painNABodyCysticNABenignNA
Ferrozzi et al[32]1995F68Upper abdominal painNAHead/bodyCysticNABenign
Sugiyama et al[33]1995M41Asymptomatic1.5UncinateCysticPDBenignNA
Steven et al[34]1994M59Asymptomatic4.0UncinateSolidPDBenign10
Melato et al[35]1993M87Upper abdominal pain20.0Body/tailCysticNABenignNA
David et al[3]1993M46Right sided abdominal pain6.0UncinateCysticNABenignNA
Urban et al[36]1992F56Right sided hip pain4.0BodyCysticDPBenignNA
Burd et al[37]1992M73Right upper quadrant abdominal pain2.0Body/tailSolidNABenignNA
Coombs et al[38]1990F74Anemia, melena7.0HeadSolid with necrotic centerNAMalignantNA
Liessi et al[39]1990F75Abdominal pain7.0HeadSolidNot resectedBenign7
Walsh et al[40]1989F35Abdominal pain, melena, anemiaNAHeadNAPDMalignant24
Eggermont et al[41]1987F40Upper abdominal pain, jaundice, weight loss10.0HeadSolid with necrotic centerPDMalignant9
Moller-Pederson et al[42]1982M60Back pain, weight loss20.0Body/tailCysticUnresectableMalignant4
Table 2 Summary of clinicopathological data from all 47 cases of pancreatic schwannoma.
n (%) or mean ± SD (range)
Age (yr)55.7 ± 15.1 (20-87)
Sex (male/female), (male %)21/26 (45%)
Symptoms1
Asymptomatic14 (30%)
Symptomatic
Abdominal pain27 (57%)
Weight loss6 (13%)
Back pain3 (6%)
Nausea/vomiting2 (4%)
Abdominal mass2 (4%)
Anemia2 (4%)
Melena2 (4%)
Jaundice1 (4%)
Location
Head19 (40%)
Head/body3 (6%)
Body10 (21%)
Body/tail7 (15%)
Tail2 (4%)
Uncinate process6 (13%)
Mean size (cm), (n = 44)6.2 ± 5.1 (1-20)
Operation
Pancreaticoduodenectomy215 (32%)
Distal pancreatectomy310 (21%)
Enucleation7 (15%)
Unresectable2 (4%)
Refused1 (2%)
Not specified12 (26%)
Histology
Malignant5 (11%)
Benign41 (87%)
Not specified1 (2%)
Nature of tumor
Solid16 (34%)
Cystic28 (60%)
Not specified3 (6%)
Mean follow-up months (n = 23)18.9 ± 15.7 (3-65)
Died of disease0 (0%)

A PubMed search of the literature indicated 41 reports including 47 patients with pancreatic schwannoma in the English literature. Details of all the 47 cases are summarized in Table 1. Table 2 summarizes the important available clinicopathological factors. The mean age of the patients was 55.7 ± 15.1 years (range 20-87 years) and the male-female ratio was 21:26. Thirty percent of patients were asymptomatic and 70% of patients were symptomatic. Symptoms included abdominal pain (57%), weight loss (13%), back pain (6%), nausea/vomiting (4%), abdominal mass (4%), melena (4%), and jaundice (4%). The symptoms did not correlate with tumor size and tumor location. The lesion was located in the pancreas head in 19 patients (40%), head and body in 3 patients (6%), body in 10 patients (21%), body and tail in 7 (15%), tail in 2 patients (4%), and uncinate process in 6 patients (13%). Mean tumor size was 6.2 ± 5.1 cm (range 1-20 cm). Treatment included pancreaticoduodenectomy for 15 patients (32%) including one portal vein reconstruction, distal pancreatectomy for 10 patients (21%) including combined transverse colon resection, enucleation for 7 patients (15%), unresectable for 2 patients (4%), refused operation for 1 patient (2%) and the detail of resection was not specified in 12 patients (26%). Enucleation was performed for 7 patients, and out of these, 3 lesions were located in the head, 2 lesions were in the uncinate process and 2 lesions were in the body. The mean tumor size in the patients who underwent enucleation was 2.7 cm (range 1.5-4.0 cm). Regarding gross appearance, 34% of patients exhibited solid tumors and 60% of patients exhibited cystic tumors. No patient died of disease with a follow-up of 15.7 mo (range 3-65 mo), although 4 (9%) patients had a malignancy. The tumor size was related to malignant tumor (13.8 ± 6.2 cm for malignancy vs 5.5 ± 4.4 cm for benign, P = 0.001) (Figure 4A) and cystic formation (7.9 ± 5.9 cm for cystic tumor vs 3.9 ± 2.4 cm for solid tumor, P = 0.005) (Figure 4B).

Figure 4
Figure 4 Analysis for relation between tumor size and malignant potential and tumor nature (solid or cystic) in all 47 cases of pancreatic schwannoma. A: Relationship between tumor size and malignancy. Larger tumor size is related to malignant tumor (13.8 ± 6.2 cm for malignancy vs 5.5 ± 4.4 cm for benign, P = 0.001); B: Relationship between tumor size and nature of tumor. Larger tumor size is related to cystic degeneration (13.8 ± 6.2 cm for cystic tumor vs 5.5 ± 4.4 cm for solid tumor, P = 0.005).

In 1910, Verocay reported a schwannoma as a true neoplasm which originated from Schwann cells, and which did not contain neuroganglion cells[1]. Since then, schwannomas have become well known as benign spindle cell tumors derived from Schwann cells that line the nerve sheaths. Schwannomas usually occur in the extremities, but can also be found in the trunk, head and neck, retroperitoneum, mediastinum, pelvis and rectum[2-4]. Pancreatic schwannomas are rare neoplasms that arise from either autonomic sympathetic or parasympathetic fibers, both of which course through the pancreas as branches of the vagus nerve[2-4].

Microscopically, a typical schwannoma is composed of 2 areas, namely Antoni A and Antoni B areas. The Antoni A area is hypercellular and characterized by closely packed spindle cells with occasional nuclear palisading and Verocay bodies, whereas the Antoni B area is hypocellular and is occupied by loosely arranged tumor cells[43]. Most of the pancreatic schwannomas reported had both Antoni A and Antoni B areas in various proportions. Degenerative or cystic changes such as calcification or hemorrhage are often recognized in the Antoni B area. These changes result from vascular thrombosis and subsequent necrosis[43]. Cystic pancreatic schwannomas can mimic the whole spectrum of cystic pancreatic lesions including: intraductal mucinous-papillary neoplasms, mucinous cystic neoplasms, serous cystic neoplasms, solid and pseudo-papillary neoplasms, lymphangiomas, and pancreatic pseudocysts. Immunohistochemically, schwannomas stain strongly positive for S-100 protein, vimentin and CD 56, while negative for other tumor markers including cytokeratin AE1/AE3, desmin, smooth muscle myosin, CD 34 and CD 117[43].

The symptoms of the reported patient cases of pancreatic schwannoma vary. Seventy percent of patients were symptomatic. Abdominal pain was the most common symptom reported (57%). Symptoms such as back pain (6%), nausea/vomiting (4%), weight loss (13%), melena (4%) and jaundice (4%) have been also reported. Thirty percent of patients were asymptomatic and the lesions were incidentally discovered on CT scans performed for other reasons.

The preoperative diagnosis of pancreatic schwannoma is very difficult, especially in cystic schwannomas. Suzuki et al[8]

reviewed imaging features of pancreatic schwannomas. The most characteristic feature on CT scan was the presence of an area of low density and/or cystic images reflecting the Antoni B component or degenerative cystic areas of the schwannoma. Contrast-enhanced CT scan showed the difference between the Antoni A and the Antoni B areas based on their vascularity, i.e., well-enhanced areas corresponding to Antoni A, and unenhanced areas corresponding to Antoni B. The CT findings correlated well with pathological features[8,19]. The MRI findings usually showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images[21]. However, other pancreatic tumors often share those imaging features, and differential diagnoses should always be considered. Ultrasound-guided Fine Needle Aspiration (EUS-FNA) biopsy has been used increasingly commonly at many institutions. This procedure may be useful for accurate preoperative diagnosis. Cytologically, schwannomas are characteristically composed of spindle-shaped cells, which possess indistinct cytoplasmic borders and wavy nuclei embedded in a fibrillary and occasionally myxoid or collagenous matrix. The Antoni A (cohesive cellular clusters) and Antoni B (loosely cohesive or poorly cellular sheets) areas are occasionally found. Immunohistochemical staining is useful for accurate diagnosis of schwannoma[12,14]. It is diffusely and strongly positive for S-100 protein. There has only been one previous report of pancreatic schwannoma diagnosed preoperatively by EUS-FNA cytology combined with immunohistochemistry[12].

Although malignant pancreatic schwannomas have been reported in 5 articles[7,38,40-42], in 3 of 5 the methods of diagnosing malignancy were inconsistent, as some previous reports pointed out[4,5]. Immunohistochemical examination was not used or was not available in these 3 patients. Walsh and Bradspigel[40] described a case of pancreatic schwannoma eroding into the bowel wall and presenting with gastrointestinal bleeding that mimicked a recurrently bleeding duodenal ulcer. Another two patients reported had disease associated with von Recklinghausen’s disease[41,42]. These could represent misdiagnosed neurofibromas that underwent malignant degeneration[4,5]. Stojanovic et al[7] reported malignant pancreatic schwannoma with node metastasis and infiltrating serosa of transverse colon. This tumor was confirmed using immunohistochemical examination. This may be the first definite report of malignant schwannoma with subsequent radical resection.

Since malignant transformation of pancreatic schwannomas is uncommon, simple enucleation is usually sufficient. A review of the treatment showed that the most common resection was pancreaticoduodenectomy (32%), followed by distal pancreatectomy (21%) and enucleation (15%). This result may account for the difficulty in accurate diagnosis of pancreatic schwannoma and relate to larger size of this tumor. Enucleation was performed for 7 patients for whom 3 lesions were located in the head, 2 lesions were in the uncinate process and 2 lesions were in the body. The mean tumor size of the patients who underwent enucleation was 2.7 cm (range 1.5-4.0 cm). Intraoperative consultation with the pathologist was carried out in most of the enucleated cases. An intraoperative frozen section should be performed, as it helps to establish the diagnosis of a benign schwannoma and avoid more radical resection. Large tumors, tumors involving portal vein, ampulla, or splenic hilum, may require a more radical resection than simple enucleation.

The present report shows the correlation between tumor size and malignant formation (Figure 4A), and tumor size and cystic degeneration (Figure 4B). Malignant schwannomas were more likely to be larger-sized compared to many other tumors. On the other hand, the particular feature of pancreatic schwannoma was that larger tumor size was related to cystic degeneration, as shown in Figure 4B. Cystic degeneration could make it difficult to diagnose pancreatic schwannoma preoperatively, because of mimicking other cystic neoplasms. Caution should be applied when diagnosing cystic neoplasm. An intraoperative frozen section may help to establish the diagnosis of a schwannoma and avoid more radical resection. To our knowledge, the present report is the first to analyze the relation among tumor size, malignant formation and cystic degeneration. Our results suggest that pancreatic schwannoma might be resected even though diagnosed preoperatively, because if schwannomas are smaller, enucleation should be oncologically adequate. However, when tumors become larger with associated bleeding risk, more invasive resection such a PD or DP might be necessary. In particular, in cases of tumors more than 10 cm in size, we should pay special attention to malignant degeneration and should perform a more extended resection. To avoid extended resection, earlier resection and accurate diagnosis are very important.

In conclusion, pancreatic schwannomas deserve attention with regard to the differential diagnosis of pancreatic lesions. Preoperative diagnosis is very difficult. Simple enucleation is adequate if this is possible to achieve. Intraoperative frozen section is useful to diagnose schwannoma.

Footnotes

Peer reviewers: Ian C Roberts-Thomson, Professor, Department of Gastroenterology and Hepatology, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville South 5011, Australia; De-Liang Fu, Professor, Department of General Surgery, 12 Wulumuqi Road (M), Shanghai 200040, China.

S- Editor Sun H L- Editor Logan S E- Editor Zhang DN

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