Figure 1
CT scan arterial phase
Mesenchymal pancreatic tumor
SectionAbdominal imaging
Case TypeClinical Cases
Authors
P. Argyropoulou, P.K. Prassopoulos
Department of Radiology, University Hospital of Alexandroupolis, Greece.
ECR 2009 - CASE OF THE DAY
Connected authors
56 years, male
Clinical History
A 56-year-old man was investigated for recurrent episodes of ileus. He underwent an abdominal CT and due to an incidental finding of the pancreas, we proceeded to an abdominal MRI and MRCP. Endocrine evaluation, tumor markers and laboratory data were unremarkable.
Imaging Findings
MRCP did not disclose any abnormal findings. There were no signs of metastatic disease.
Fig. 1: CT scan - arterial-phase, demonstrates a hypodense mass in the body and the tail of the pancreas. Fig. 2: CT scan - venous-phase: The contrast between the mass and the normal parenchyma is diminished. Fig. 3: Delayed enhancement of the mass is observed. Fig. 4: Contrast enhanced, fat saturated, T1-weighted (TR/ TE/ flip angle, 9,2/3,8/150) MRI, arterial phase: The mass is hypointense relative to the pancreatic parenchyma. Fig. 5: Contrast enhanced, fat saturated, T1-weighted (TR/ TE/ flip angle, 9,2/3,8/150) MRI, venous phase, the signal intensity of the mass increases. Fig. 6: Contrast enhanced, fat saturated, T1-weighted (TR/ TE/ flip angle, 9,2/3,8/150) MRI delayed phase, 5 minutes after contrast medium administration: The mass appears hyperintense relative to the pancreatic parenchyma. Fig. 7: T2-weighted MRI at the level of the body and the tail of the pancreas: The mass is slightly hyperintense relative to the pancreas. Fig. 8: T2-weighted MRI, 2cm cranially of the previous image, shows an exophytic, sharply marginated component of the mass.
Potential diagnoses were pancreatic carcinoma, islet cell tumor, mesenchymal pancreatic tumor, autoimmune pancreatitis, and solid papillary epithelial tumor.
A distal pancreatectomy with splenectomy was performed, revealing an encapsulated mass of the pancreas. The cut surface of the tumor had a pale yellow colour. The pathologic examination disclosed a schwannoma with a type Antoni A pattern. S-100 immunohistochemistry staining was positive in the Schwann cells.
Fig. 1: CT scan - arterial-phase, demonstrates a hypodense mass in the body and the tail of the pancreas. Fig. 2: CT scan - venous-phase: The contrast between the mass and the normal parenchyma is diminished. Fig. 3: Delayed enhancement of the mass is observed. Fig. 4: Contrast enhanced, fat saturated, T1-weighted (TR/ TE/ flip angle, 9,2/3,8/150) MRI, arterial phase: The mass is hypointense relative to the pancreatic parenchyma. Fig. 5: Contrast enhanced, fat saturated, T1-weighted (TR/ TE/ flip angle, 9,2/3,8/150) MRI, venous phase, the signal intensity of the mass increases. Fig. 6: Contrast enhanced, fat saturated, T1-weighted (TR/ TE/ flip angle, 9,2/3,8/150) MRI delayed phase, 5 minutes after contrast medium administration: The mass appears hyperintense relative to the pancreatic parenchyma. Fig. 7: T2-weighted MRI at the level of the body and the tail of the pancreas: The mass is slightly hyperintense relative to the pancreas. Fig. 8: T2-weighted MRI, 2cm cranially of the previous image, shows an exophytic, sharply marginated component of the mass.
Potential diagnoses were pancreatic carcinoma, islet cell tumor, mesenchymal pancreatic tumor, autoimmune pancreatitis, and solid papillary epithelial tumor.
A distal pancreatectomy with splenectomy was performed, revealing an encapsulated mass of the pancreas. The cut surface of the tumor had a pale yellow colour. The pathologic examination disclosed a schwannoma with a type Antoni A pattern. S-100 immunohistochemistry staining was positive in the Schwann cells.
Discussion
Schwannomas are most commonly located in the extremities, the trunk, head and neck regions. A pancreatic location of the tumor, arising from sympathetic and parasympathetic nervous fibers, is extremely rare [1]. Schwannomas are well encapsulated masses and their imaging appearance correlates with their histology. Those with a predominant Antoni B pattern, characterized by loose texture and lack of fibrillar background, appear as cystic or multiseptated masses with minimal or no enhancement, while those with a predominant Antoni A pattern, composed of dense cellular elements and a reticular vascular component of the stroma, appear as solid enhancing masses [1].
Pancreatic adenocarcinoma may similarly exhibit a late enhancement due to the slower wash-out as compared with the normal pancreatic parenchyma. However, it typically appears as a poorly defined, infiltrative mass with vascular involvement and metastatic liver disease, especially when an extensive mass is present as in our case.
Islet cell tumors are hypervascular and expected to show a strong contrast enhancement in the arterial phase. Delayed enhancement has only been reported in malignant islet tumors of scirrhous type, which are usually associated with metastases or invasion of vascular structures and surrounding parenchyma [2].
Autoimmune pancreatitis presents as a diffuse or focal enlargement of the pancreas, associated with irregular narrowing of the main pancreatic duct in most of the cases. Elevated levels of serum gamma-globulin, IgG and non-specific autoantibodies are expected.
Solid papillary epithelial tumors usually involve the pancreatic tail and may reach considerable size. However, they almost exclusively affect young women and may contain areas of cystic degeneration and necrosis.
In our case, the exophytic component of the mass, the sharp margin, the delayed enhancement on both multiphasic CT and MRI [3, 4] and the proximity to the celiac axis, where the pancreatic nervous plexus is located [5], were strong indicators of a mesenchymal tumor, probably of neural origin.
In conclusion, the delayed enhancement of a sharply marginated, non infiltrative, solid pancreatic mass, with no signs of malignancy, may be considered as a diagnostic indicator of type Antoni A, schwannoma.
Pancreatic adenocarcinoma may similarly exhibit a late enhancement due to the slower wash-out as compared with the normal pancreatic parenchyma. However, it typically appears as a poorly defined, infiltrative mass with vascular involvement and metastatic liver disease, especially when an extensive mass is present as in our case.
Islet cell tumors are hypervascular and expected to show a strong contrast enhancement in the arterial phase. Delayed enhancement has only been reported in malignant islet tumors of scirrhous type, which are usually associated with metastases or invasion of vascular structures and surrounding parenchyma [2].
Autoimmune pancreatitis presents as a diffuse or focal enlargement of the pancreas, associated with irregular narrowing of the main pancreatic duct in most of the cases. Elevated levels of serum gamma-globulin, IgG and non-specific autoantibodies are expected.
Solid papillary epithelial tumors usually involve the pancreatic tail and may reach considerable size. However, they almost exclusively affect young women and may contain areas of cystic degeneration and necrosis.
In our case, the exophytic component of the mass, the sharp margin, the delayed enhancement on both multiphasic CT and MRI [3, 4] and the proximity to the celiac axis, where the pancreatic nervous plexus is located [5], were strong indicators of a mesenchymal tumor, probably of neural origin.
In conclusion, the delayed enhancement of a sharply marginated, non infiltrative, solid pancreatic mass, with no signs of malignancy, may be considered as a diagnostic indicator of type Antoni A, schwannoma.
Differential Diagnosis List
Mesenchymal pancreatic tumor / pancreatic schwannoma of the Antoni A type
Final Diagnosis
Mesenchymal pancreatic tumor / pancreatic schwannoma of the Antoni A type
References
[1] Ferrozzi F, Bova D, Garlaschi G. (1995) Pancreatic schwannoma. Report of three cases. Clin Radiol 50: 492-495. (PMID: 7614798)
[2] Ichikawa T, Peterson MS, Federle MP et al. (2000) Islet tumors of the pancreas: Biphasic CT versus MR imaging in tumor detection. Radiology 216(1): 163-71. (PMID: 10887243)
[3] Novellas S, Chevallier P, Saint Paul MC, Gugenheim J, Bruneton JN (2005) MRI features of a pancreatic schwannoma. Clin Imaging 29(6): 434-436. (PMID: 16274899)
[4] Morita S, Okuda J, Sumiyoshi K, Taketani M, Moriguchi A, Katsu K, Tanigawa N (1999) Pancreatic schwannoma. Report of a case. Surg Today 29: 1093-1097. (PMID: 10554337)
[5] A.L. Baert, G. Delorme and L. Van Hoe (1999) Radiology of the Pancreas, 2nd ed. Springer, Berlin Heidelberg New York.
Case information
| URL: | https://www.eurorad.org/case/7476 |
| DOI: | 10.1594/EURORAD/CASE.7476 |
| ISSN: | 1563-4086 |
Figure 2
CT scan venous phase
Figure 3
CT scan delayed phase
Figure 4
Contrast enhanced (arterial phase), fat saturated, T1
Figure 5
Contrast enhanced (venous phase), fat saturated, T1
Figure 6
Contrast enhanced (late phase - 5 min), fat saturated, T1
Figure 7
T2-weighted
Figure 8
T2-weighted
CT scan arterial phase
CT scan venous phase
CT scan delayed phase
Contrast enhanced (arterial phase), fat saturated, T1
Contrast enhanced (venous phase), fat saturated, T1
Contrast enhanced (late phase - 5 min), fat saturated, T1
T2-weighted
T2-weighted
