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Year : 2018  |  Volume : 14  |  Issue : 10  |  Page : 793-795

Pancreatic primitive neuroectodermal tumor: Focus on radiological features and differential diagnosis – A case report and literature review


1 Department of Radiology, Xiangya Hospital, Central South University, Changsha 410008, Hunan, P.R. China
2 Department of Pathology, Xiangya Hospital, Central South University, Changsha 410008, Hunan, P.R. China

Date of Web Publication24-Sep-2018

Correspondence Address:
Wenzheng Li
Department of Radiology, Xiangya Hospital, Central South University, 87# XiangYa Road, Changsha 410008, Hunan
P.R. China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-1482.189399

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 > Abstract 


Primitive neuroectodermal tumor (PNET) is an exceedingly rare type of malignant tumor. The diagnosis of pancreatic PNET is usually challenging for radiologists and surgeons, especially when an accurate preoperative diagnosis is needed. Herein, we report a case of a 36-year-old patient with a mass diagnosed as PNET in the head of the pancreas and present a literature review. Compared to previous literature reports, there were some imaging features observed by computed tomography (CT) in our case that might be helpful for a relatively accurate preoperative diagnosis. PNET should be considered preoperatively for soft-tissue neoplasms of the pancreas when the diagnosis of more common pancreatic tumors is not favored by signs in CT, especially in pediatric and adolescent populations. This case is the 20th case of pancreatic PNET reported in literature.

Keywords: Computed tomography, pancreatic tumor, primitive neuroectodermal tumor


How to cite this article:
Liu W, Xiao D, Yi X, Li W. Pancreatic primitive neuroectodermal tumor: Focus on radiological features and differential diagnosis – A case report and literature review. J Can Res Ther 2018;14, Suppl S3:793-5

How to cite this URL:
Liu W, Xiao D, Yi X, Li W. Pancreatic primitive neuroectodermal tumor: Focus on radiological features and differential diagnosis – A case report and literature review. J Can Res Ther [serial online] 2018 [cited 2020 Dec 1];14:793-5. Available from: https://www.cancerjournal.net/text.asp?2018/14/10/793/189399




 > Introduction Top


Primitive neuroectodermal tumor (PNET) is an exceedingly rare type of malignant tumor occurring predominantly in the pediatric and adolescent populations.[1] It can occur in the pancreas and accounts for 0.3% of all primary pancreatic neoplasms.[2],[3] To the best of our knowledge, only 19 pancreatic PNET cases have been reported worldwide to date.[4] Due to its rare incidence and low accumulated experience, its diagnosis is a great challenge for radiologists and surgeons. Recently, we encountered a case of pancreatic PNET with some radiological features that might be helpful for a relatively accurate preoperative diagnosis. The clinicopathological features are also discussed.


 > Case Report Top


A 36-year-old male patient was admitted to our hospital with obvious upper abdominal pain and jaundice for 1 month. There was no significant medical or surgical history. The patient was in a good general condition, and physical examination showed no obvious abnormalities except for mild upper abdominal tenderness. Laboratory examination suggested mild obstructive jaundice and elevated serum cancer antigen 19-9 level (92.61 U/L). Chest radiograph was normal.

An abdominal and pelvic contrast-enhanced computed tomography was done for the evaluation of pain abdomen, and a pancreatic mass was discovered. The mass was located in the pancreatic head (size, 6.3 cm × 3.6 cm × 4.8 cm) and showed a round to lobulated appearance, with well-defined margins [Figure 1]. The lesion displaced the adjacent tissue, including the superior mesenteric vein (SMV), without obvious signs of infiltration. However, the left margin of the tumor was close to the right edge of the SMV and the initial part of the portal vein; thus, venous infiltration could not be completely ruled out. The mass appeared mildly heterogeneous (with an attenuation value of about 47 HU) on pre-enhanced images with heterogeneous mild to moderate enhancement after contrast medium administration. No calcification was detected. No other lesions were found in the abdomen and pelvis. History, examination, and imaging neither showed any metastasis anywhere nor detected any other mass anywhere to suggest a primary PNET somewhere else in the body metastasizing to the pancreas. Based on the above results, the lesion was initially diagnosed as a primary unspecified pancreatic tumor. According to imaging findings, typical pancreatic cancer (PC) and tumors with a rich blood supply, such as pancreatic neuroendocrine tumor (PNT) and solid pseudopapillary tumor (SPT), were ruled out (as it is discussed in the “discussion” section). The primary mesenchymal tumors of the pancreas were considered in differential diagnosis, but a definite preoperative diagnosis could not be made. A week later, the patient underwent exploratory laparotomy. During the operation, a mass with medium texture and no obvious capsule was palpable in the pancreatic head and neck. The mass was close to the right edge of the SMV and the portal vein and could not be separated from the vein. Intraoperative frozen section examination of the pancreatic mass suggested a small round cell malignancy, likely to be PNET. As radical resection was impossible, a Roux-en-Y choledochojejunostomy was performed. The postoperative pathological study demonstrated that the tumor was composed of atypical small round cells with scant cytoplasm arranged in nests with fibrovascular stroma [Figure 1]f. Immunostaining was positive for Ki-67 (20%), vimentin, β-catenin, alpha-1-antichymotrypsin, CD99, and human soluble protein-100 and negative for CD10, CD56, chromogranin A, cytokeratin pan, lens culinaris agglutinin, synuclein, CD1a, carcinoembryonic antigen, melanoma antibodies clone HMB45, nestin, neuron-specific enolase, CD31, CD34, CD57, cytokeratin 19, factor VIII, and myelin basic protein. Based on the morphological and immunohistochemical features, a diagnosis of PNET was established.
Figure 1: Diagnostic images of the mass located in the pancreatic head. Computed tomography images from (a) Pre-enhanced phase, (b) artery phase, (c) venous phase computed tomography. Reconstructed (d) coronary and (e) sagittal computed tomography images. (f) H and E staining of the tumor (×200)

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The postoperative course was uneventful. However, the patient refused adjuvant radiotherapy and chemotherapy and was discharged 2 weeks later after the operation. One month later, the patient underwent an abdominal ultrasound examination. Unfortunately, the pancreatic mass was found significantly increased and invading to surrounding tissues (superior mesenteric artery, celiac artery), accompanied by multiple liver metastases. The patient grew worse and died 2 months later because of severe infection and multiple organ failure.


 > Discussion Top


PNET belongs to the Ewing sarcoma family of tumors, which exhibit a neural phenotype and express MIC2 protein (CD99).[5] It is extremely rare in organs containing neuroendocrine cells such as the pancreas. Due to the resulting lack of experience, especially the absence of a summary of radiological and clinicopathological characteristics, definite preoperative diagnosis of pancreatic PNET is usually impossible.

Combined with the published literature,[2],[6],[7] some imaging features may contribute to enabling a relatively reliable preoperative diagnosis, including a well-defined margin, mildly heterogeneous and relatively heterogeneous mild to moderate enhancement, lack of calcification, a tendency for the soft-tissue component to displace the adjacent structures rather than obviously invading or encasing them, and no retroperitoneal lymphadenopathy. Therefore, appropriate integration of the radiological and clinicopathological findings is necessary for a feasible successful preoperative diagnosis of pancreatic PNET.

In general, the main differential diagnosis candidates for pancreatic PNET include primary mesenchymal tumors, atypical PC and SPT, undifferentiated small cell carcinoma, pancreatoblastoma, PNTs, and occasionally lymphoma.[3] However, certain imaging features may help a radiologist to differentiate between PNET and such tumors. Although PC can demonstrate atypical imaging findings, it always shows a relatively low enhancement appearance, with several obvious signs of malignancy, including liquefactive necrosis, ill-defined margin, metastasis, and the invasion of adjacent structures or vessels. SPT usually has cystic and solid components with marked enhancement and occasionally calcification. It is very difficult to differentiate PNET from other primary mesenchymal tumors of the pancreas by imaging, especially other small cell tumors. Pathological, immunohistochemical, and cytogenetic comprehensive analyses are necessary for qualitative diagnosis. The definitive diagnosis of PNET can be made based on the morphological and immunohistochemical features. Notably, CD99 or p30/32MIC2, the product of the MIC2 gene on the X chromosome, is generally present in these tumors although not specific for PNET or Ewing's sarcoma.[5],[8],[9]

In general, the prognosis of pancreatic PNET is poor, with a 5-year survival rate of approximately 50%.[10] However, the prognosis of this disease can become extremely poor due to a high degree of malignancy, especially when the radical operation cannot be performed. Our patient is such a case.


 > Conclusion Top


Some imaging features may contribute to enabling a relatively reliable preoperative diagnosis of pancreatic PNET. However, these imaging features are still nonspecific. Even so, PNET should be considered preoperatively for soft-tissue neoplasms of pancreas when the diagnosis of a more common tumor, such as PC, is not favored based on the imaging signs in CT, especially in pediatric and adolescent populations.

Financial support and sponsorship

This study was supported by the Freedom Exploration Program of Central South University (No. 2011QNZT153), the Natural Science Foundation of Hunan Province (No. 14JJ6001), and the Foundation of Science and Technology Department of Hunan Province (No. 2014SK3268).

Conflicts of interest

There are no conflicts of interest.



 
 > References Top

1.
Carvajal R, Meyers P. Ewing's sarcoma and primitive neuroectodermal family of tumors. Hematol Oncol Clin North Am 2005;19:501-25, vi-vii.  Back to cited text no. 1
    
2.
Mao Y, Sang X, Liang N, Yang H, Lu X, Yang Z, et al. Peripheral primitive neuroectodermal tumors arising in the pancreas: The first case report in Asia and a review of the 14 total reported cases in the world. Hepatobiliary Surg Nutr 2013;2:51-60.  Back to cited text no. 2
    
3.
Kim JY, Song JS, Park H, Byun JH, Song KB, Kim KP, et al. Primary mesenchymal tumors of the pancreas: Single-center experience over 16 years. Pancreas 2014;43:959-68.  Back to cited text no. 3
    
4.
Teixeira U, Goldoni M, Unterleider M, Diedrich J, Balbinot D, Rodrigues P, et al. Primitive neuroectodermal tumor of the pancreas: A case report and review of the literature. Case Rep Surg 2015;2015:276869.  Back to cited text no. 4
    
5.
de Alava E, Gerald WL. Molecular biology of the Ewing's sarcoma/primitive neuroectodermal tumor family. J Clin Oncol 2000;18:204-13.  Back to cited text no. 5
    
6.
Hari S, Jain TP, Thulkar S, Bakhshi S. Imaging features of peripheral primitive neuroectodermal tumours. Br J Radiol 2008;81:975-83.  Back to cited text no. 6
    
7.
Changal KH, Mir MH, Azaz SA, Qadri SK, Lone AR. Primitive neuroectodermal tumour of pancreas; second case from Asia. Malays J Med Sci 2014;21:65-9.  Back to cited text no. 7
    
8.
Movahedi-Lankarani S, Hruban RH, Westra WH, Klimstra DS. Primitive neuroectodermal tumors of the pancreas: A report of seven cases of a rare neoplasm. Am J Surg Pathol 2002;26:1040-7.  Back to cited text no. 8
    
9.
Weidner N, Tjoe J. Immunohistochemical profile of monoclonal antibody O13: Antibody that recognizes glycoprotein p30/32MIC2 and is useful in diagnosing Ewing's sarcoma and peripheral neuroepithelioma. Am J Surg Pathol 1994;18:486-94.  Back to cited text no. 9
    
10.
Hashimoto H, Enjoji M, Nakajima T, Kiryu H, Daimaru Y. Malignant neuroepithelioma (peripheral neuroblastoma). A clinicopathologic study of 15 cases. Am J Surg Pathol 1983;7:309-18.  Back to cited text no. 10
    


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