Yolk sac tumour of the mediastinum

Definition

A tumour showing an architecture resembling the yolk sac.

Synonyms

Endodermal sinus tumour

Epidemiology

There is a peak incidence in infants and young children, predominantly females: the tumour is usually pure yolk sac. Post-puberty, tumours are usually mixed germ cell tumours; they occur exclusively in males.

Histopathology

The tumour cells are small with scant pale cytoplasm. Nuclei are round with small nucleoli. The architecture is variably microcystic, macrocystic, glandular, alveolar, pseudopapillary, myxoid, hepatoid, enteric, polyvesicular, vitelline or solid. Up to 75% of yolk sac tumours show Schiller-Duval bodies. There are often hyaline PAS-positive droplets.

Immunohistochemistry

	AFP	variably positive0
	Low MW cytokeratin	positive0
	Vimentin	may be focally positive0

Differential diagnosis

In adults, if the tumour cells are large and the architecture solid, embryonal carcinoma or germinoma.

Prognosis

Prognosis is dependent on the resectability of the tumour. If resectable, there is a long term survival of 90% in children. In adults, most tumours have metastasized and are fatal.

References

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

This page last revised 20.1.2006.