• Abundant anucleated squamous cells
• Multinucleated giant cells
• Mature lymphocytes in a background of keratinaceous debris
• A lack of neoplastic cells

*Absence of lymphoepithelial cyst cytology on EUS does not exclude diagnosis*

Etiology is currently unknown. Hypotheses for histogenesis of lymphoepithelial cysts include:

1. squamous metaplasia of pancreatic ducts with subsequent cystic transformation
2. ectopic pancreatic tissue within a peripancreatic lymph node
3. epithelial remnants within peripancreatic lymph nodes
4. ectopic remnants of a brachial cleft cyst that are misplaced and fused with the pancreas during embryogenesis

Case 1: 37-year-old M with history of testicular seminoma/embryonal testicular cancer who presented with an incidentally found peripancreatic cystic lesion. FNA of lesion demonstrated anucleated squamous cells and rare macrophages consistent with lymphoepithelial cyst.

Left: Axial contrast-enhanced arterial phase CT demonstrates a cystic mass of water-density adjacent to left kidney.
Right: Axial contrast-enhanced venous phase CT demonstrates multiple cystic masses of water-density adjacent to pancreas and left kidney.

Left: Axial contrast-enhanced arterial phase CT demonstrate large mass (9.5 x 6.3 cm) of water-density adjacent to head of pancreas. The pancreas enhances normally with normal-sized pancreatic duct.
Right: Sagittal multi-planar reconstruction contrast-enhanced arterial phase CT demonstrates large mass adjacent to head of pancreas.

3DCT demonstrates large mass adjacent to pancreatic head.

Case 2: 70-year-old M with incidentally found pancreatic lesion. FNA of lesion demonstrated proteinaceous keratinaceous debris and rare histiocytes. Patient underwent distal pancreatectomy with pathological confirmation of lymphoepithelial cyst.

3DCT coronal and axial views demonstrate cyst near pancreatic tail with single thick septation.

Top: Axial and sagittal contrast-enhanced arterial phase CT demonstrate 3.9 cm cyst with a thick septation in the tail of pancreas.
Right: Axial venous phase CT demonstrates pancreatic cyst with a thick septation.

Pathology demonstrates a cyst lined by squamous epithelium, with lymphocytes and germinal centers in the cyst wall. Keratin debris is also seen.

Case 3: 47 yo M with history of alcohol abuse presenting with weight loss and epigastric pain. CT scan demonstrated cyst in tail of pancreas. The lesion was resected and pathology confirmed diagnosis of lymphoepithelial cyst.

Left: Axial contrast-enhanced arterial phase CT demonstrates cystic lesion near tail of pancreas. No evidence of acute pancreatitis.
Right: Axial contrast-enhanced venous phase CT demonstrates well-defined cystic lesion of water density with no solid components.

Left x2: Coronal and sagittal contrast-enhanced arterial phase CT demonstrate cystic lesion near tail of pancreas. 
Bottom: Coronal 3DCT demonstrates cystic lesion near tail of pancreas

Case 4: 62 year old M with incidentally discovered pancreatic cyst. Pancreatic cyst fluid did not show evidence of malignant cells and was initially followed. Enlarging cyst prompted surgical resection. Pathology confirmed diagnosis of lymphoepithelial cyst

Axial contrast-enhanced arterial phase CT demonstrates cystic mass near tail of pancreas and anterior to left kidney. Cross sectional diameter measured 10.1 cm. Tiny calcification adjacent to lesion was visualized (arrowhead).

Pathology demonstrates a cyst lined by squamous epithelium, with lymphocytes and marked hyalinization in the cyst wall.

Coronal 3D CT demonstrates a large pancreatic cyst near tail of pancreas. Cystic lesion is well-defined, water density, with no septations.

Case 5: 54 yo M with abdominal pain, incidentally found to have 3 cm pancreatic lesion. FNA demonstrated predominantly acute inflammation. He underwent resection of the lesion. Pathology confirmed epidermoid cyst with surrounding lymphoid reaction.

Coronal 3D CT demonstrates pancreatic cyst.

Left: Axial contrast enhanced arterial phase CT demonstrates pancreatic head cyst, abutting SMA. 
Middle: Axial arterial phase CT demonstrates pancreatic head cyst, abutting SMV.
Right: Axial venous phase CT demonstrates pancreatic cyst

Case 6: 62-year-old M with an incidentally found pancreatic lesion near tail of pancreas. Patient underwent distal pancreatectomy with pathological confirmation of lymphoepithelial cyst.

Left: Axial contrast-enhanced arterial phase CT demonstrates cystic lesion in tail of pancreas, near splenic vasculature.Right: Axial contrast-enhanced venous phase CT demonstrates 2.0 cm cystic lesion in tail of pancreas.

FNA of lesion demonstrated few epithelial cells with focal atypia in background of acellular debris, macrophages, and lymphocytes, consistent with cyst contents.

3D Coronal contrast-enhanced CT demonstrates cystic lesion in tail of pancreas in close proximity to splenic vasculature

Case 7: 73 yo M with incidentally discovered pancreatic cyst.

3D CT demonstrates cystic mass with thin septations near tail of pancreas

The lesion was resected (above: gross specimen) and found to be a lymphoepithelial cyst.

Left: Axial contrast-enhanced arterial phase CT demonstrates 4 cm cystic lesion near tail of pancreas. Thin septations are visible.
Right: Axial contrast-enhanced venous phase CT demonstrates lesion

Pathology confirmed a cyst lined by squamous epithelium with lymphocytes and germinal centers in the cyst wall. Adjacent uninvolved pancreatic parenchyma shows no diagnostic findings.

Case 8: 56 yo M with incidentally found pancreatic cyst. CT demonstrated 5.5 cm x 4.0 xm pancreatic cyst near tail of pancreas. He underwent distal pancreatectomy.

Pathology demonstrates a cyst (luminal side indicated by arrow) lined by lymphoid tissue with overlying superficial squamous epithelium.

Right: Axial contrast-enhanced arterial phase CT demonstrates cystic lesion arising from tail of pancreas, abutting spleen and left kidney.
Left: Axial contrast-enhanced venous phase CT demonstrates pancreatic cyst.

• Nam SJ, Hwang HK, Kim H et al. Lymphoepithelial cysts in the pancreas: MRI of two cases with emphasis of diffusion-weighted imaging characteristics. Journal of Magnetic Resonance Imaging 2010; 32(3):692-696.
• Basturk O, Coban I, Adsay NV. Pancreatic Cysts: Pathologic Classification, Differential Diagnosis, and Clinical Implications. Archives of Pathology & Laboratory Medicine 2009; 133( 3):423-438.
• Fukukura Y, Inoue H, Miyazono N et al. Lymphoepithelial Cysts of the Pancreas: Demonstration of Lipid Component Using CT and MRI. Journal of Computer Assisted Tomography 1998; 22(2):311-313.
• Neyman E, Georgiades C, Horton K et al. Lymphoepithelial cyst of the pancreas—evaluation with multidetector CT. Clinical Imaging 2005; 29(5):345-347.
• Karim Z, Walker B, Lam EC. Lymphoepithelial cysts of the pancreas: The use of endoscopic ultrasound-guided fine-needle aspiration in diagnosis. Can J Gastroenterol 2010; 24(6): 348–350.

Acknowledgements: Swati Deshmukh, MD
Karen M. Horton, MD
Ralph H. Hruban, MD
Barish H. Edil, MD
Christopher L. Wolfgang, MD
Richard D. Schulick, MD
and Elliot K. Fishman, MD