Thymic low grade metaplastic carcinoma

Synonym

Biphasic thymoma, mixed polygonal and spindle cell type3

 

These tumours closely resemble thymoma with pseudosarcomatous stroma. However, the epithelial component is described as carcinomatous with variable atypia and mitotic activity. the spindle cell component shows a gradual transition from the epithelial component. Moreover, the spindle cell component is positive for cytokeratins and for EMA. There may be mesenchymal metaplasia with expression of actin, desmin, or neural markers (chromogranin, S-100 or GFAP).

Immunohistochemistry

 

 

epithelial component

spindle cell component

 

cytokeratins

positive1

positive1

EMA

positive1

positive1

vimentin

positive1

positive1

actin

2/41

2/41

Chromogranin

1/41

1/41

S-100

1/41

1/41

GFAP

1/41

1/41

NSE

1/41

1/41

     

Differential diagnosis

Prognosis

One of four patients developed a recurrence.

References

1Yoneda, S., A. Marx, et al. (1999). "Low-grade metaplastic carcinomas of the thymus: biphasic thymic epithelial tumors with mesenchymal metaplasia--an update." Pathol Res Pract 195(8): 555-63.

2Shimosato Y et al. Tumors of the mediastinum. In: Rosai J, Sobin LH, eds. Atlas of Tumor Pathology. 3rd Edn. Armed Forces Institute of Pathology 1997;93-115