[Primary malignant teratoma of the thyroid. Two cases involving immunohistochemical and ultrastructural studies].

Two cases of primary malignant teratoma of the thyroid are reported. The first case, which occurred in a 21-year-old female, was mostly composed of tumoral neural tissue and foci of foetal cartilage. The patient died with lung metastases within 5 months after the first symptoms. The second case, which occurred is a 8-year-old infant female, had epithelial and mesenchymal components without neural tissue. This case had a better prognosis with survival of four years after initial diagnosis. The different tumoral components were identified by a thorough histopathological examination of the thyroidectomy with immunological and ultrastructural studies. As for other teratomas, presence of immature neural tissue bore a poor prognosis. The clinical, histopathological features and the histogenesis of this rare tumour are described and literature is reviewed.