Thymic sarcomatoid carcinoma (carcinosarcoma)

Definition

A thymic carcinoma which is composed wholly or partly of a sarcomatous component.

Synonym

Carcinosarcoma, spindle cell thymic carcinoma

Epidemiology

This tumour accounts for 7% of thymic carcinomas. It occurs in late adulthood.

Macroscopic appearances

The tumour is not encapsulated. There may be necrosis or haemorrhage. There is often invasion of adjacent structures and metastasis to lymph nodes and lung.

Histopathology

The carcinomatous and sarcomatoid components are closely admixed and the carcinomatous component may only be apparent on immunohistochemistry. If morphologically apparent, the carcinomatous component is poorly differentiated with nuclear pleomorphism. There may be squamous differentiation. The sarcomatous component may show skeletal muscle, osteosarcomatous or cartilaginous differentiation. Coagulative necrosis is common.

There may be an associated type A thymoma.

"Spindle cell thymic carcinoma" is probably a variant, the spindle cells showing only epithelial immunoreactivity.

Immunohistochemistry

 

Cytokeratin

positive in carcinomatous component, variable in sarcomatoid component0, 3/32

 
 

EMA

positive in carcinomatous component, variable in sarcomatoid component0, 1/32

 
 

CD5

negative0, 0/32

 

Chromogranin

0/32

Synaptophysin

0/32

bcl-2

2/32

p53

2/32

Desmin
Actin
Myogenin
MyoD1

variably positive in rhabdomyosarcomatous component0

   

Differential diagnosis

Prognosis

This is an aggressive tumour with most patient dying within three years.

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.

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

This page last revised 11.1.2006.

©SMUHT/PW Bishop