Thymic lymphoepithelioma-like carcinoma

Definition

A thymic carcinoma identical to the lymphoepithelioma-like carcinoma of the upper respiratory tract. The role of EBV in the aetiology is not yet certain.

Epidemiology

There is a bimodal age distribution, with a first peak in the second decade. Cases in children have been reported1.

Clinical features

There is no association with myasthenia gravis but hypertrophic osteoarthropathy has been reported in children.

Radiology

Macroscopic appearances

The tumour is usually incompletely encapsulated.

Histopathology

The epithelial cells form a syncytial pattern. Nuclei are large with very prominent nucleoli. The lymphocytic component may be intimately admixed or form small clusters. It consists of a mix of lymphocytes and plasma cells. There may be an infiltrate of eosinophils and granulomas may occur.

Undifferentiated carcinoma positive for EBV, with a dense fibrous stroma but lacking a significant lymphoid component is provisionally included in this category.

Immunohistochemistry

 

Tumour cells

 
 

Cytokeratin

2/22

 

AE1

positive0,3

 

AE3

negative0,3

 

CK7

negative0

 

CK20

negative0

 

EMA

2/22

 

bcl-2

often positive0, 2/22

 

CD5

focal or negative0, 2/22

 

Chromogranin

0/22

Synaptophysin

0/22

p53

0/22

   

Lymphocytes

CD1a

negative0

CD3

positive0

CD5

positive0

CD20

a minority B-cell component is positive0

CD99

negative0

TdT

negative0

   

Molecular pathology

Half the cases show evidence of EBV infection, with a higher proportion in childhood and teenage cases.

Differential diagnosis

Management

Prognosis

The prognosis is poor with an average survival of 16 months, irrespective of the EBV status.

References

0 Tumours of the Lung, Pleura, Thymus and Heart. WHO Classification of Tumours. IARC Press 2004.

1 J Rosai et al. Histological typing of tumours of the thymus. WHO International histological classification of tumours. Springer-Verlag, second edition, 1999.

2Chalabreysse, L., B. Etienne-Mastroianni, et al. (2004). "Thymic carcinoma: a clinicopathological and immunohistological study of 19 cases." Histopathology 44(4): 367-74.

3 Nonaka D, Henley JD, Chiriboga L, et al. Diagnostic utility of thymic epithelial markers CD205 (DEC205) and Foxn1 in thymic epithelial neoplasms. Am J Surg Pathol 2007; 31:1038-44

This page last revised 6.1.2006.

©SMUHT/PW Bishop