Thymic epidermoid non-keratinising carcinoma

Definition

A thymic carcinoma composed of large atypical epithelial cells, lacking overt keratinisation. This is not a separate category in the current WHO classification but is included with keratinising squamous carcinoma.

Histopathology

Similar to thymic squamous cell carcinoma but lacks overt keratinisation. Lobulation is absent or less well developed than in thymic squamous cell carcinoma.

Immunohistochemistry

	Cytokeratin	4/42
	EMA	4/42
	bcl-2	4/5 (not clear if one of these cases was keratinising)2
	CD5	almost always positive, 3/5 (not clear if one of these cases was keratinising)2
	Chromogranin	positive in about 50% of cases, 3/5 (not clear if one of these cases was keratinising)2
	Synaptophysin	positive in about 50% of cases, 3/5 (not clear if one of these cases was keratinising)2
	p53	3/5 (not clear if one of these cases was keratinising)2

Differential diagnosis

• Type B3 thymoma: negative for CD5, chromogranin and synaptophysin.

References

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.

This page last revised 6.1.2006.

©SMUHT/PW Bishop