Thymic basaloid carcinoma

Definition

A thymic carcinoma composed of basaloid cells showing peripheral palisading.

Synonym

Basaloid squamous cell carcinoma of the thymus.

Epidemiology

The literature contains only ten reported cases0.

Clinical features

There is no association with paraneoplastic autoimmune conditions.

Radiology

Macroscopic appearances

These tumours often present as a mural nodule within a multilocular thymic cyst.

Histopathology

The basaloid cells with a high N/C ratio, form lobules with peripheral palisading. There is generally an absence of keratinisation, although some squamous differentiation with keratinisation may occur at the centre of tumour nests. There is a high mitotic rate. Perivascular spaces may be prominent. Cystic spaces may contain PAS+/mucicarmine- stromal mucin. Sometimes there is deposition of basement membrane like material to form eosinophilic globules.

Immunohistochemistry

	Cytokeratins	positive0
	EMA	positive0
	CD5	may be positive0
	S-100	negative0
	NSE	negative0
	Chromogranin	negative0
	Synaptophysin	negative0

Ultrastructure

Differential diagnosis

Metastatic basaloid carcinoma from the respiratory tract.
Neuroendocrine carcinoma.

Management

Prognosis

30% of cases show metastases, often to lung or liver.

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.

This page last revised 6.1.2006.