Yolk sac tumour arising in mature teratoma in the parapharyngeal space

Yolk sac tumour is germ cell tumour commonly found in children and infants under three years of age in its pure form with a good prognosis. The commonest location for the yolk sac tumour is gonads i.e. testis and gonads. Yolk sac tumour is rarely reported in extra- gonadal locations. Parapharyngeal space is an uncommon site for mature teratoma and very few cases have been reported in adults and children. Malignant transformation in a mature teratoma in the extragonadal sites has been reported but development of yolk sac tumour has not been reported so far in the world literature. We report to our knowledge, the only and first case of yolk sac tumour arising in a mature teratoma presenting as a parapharyngeal mass in a four year old male child.