[Metastasis from one tumor to another]

Tumour in tumour metastasis. The occurrence of more than one primary tumour in the same person is uncommon, nevertheless metastasis of one tumour to another is an extraordinary event. The malignant tumour usually metastasizes in a benign tumour, however a metastatic deposit within a malignant tumour is described. In the present study the literature is briefly reviewed and 43 new cases are described: in 38 the host neoplasm is a benign one, and in 4 is a malignant tumour. In the last case the metastases are present both in a malignant and in a benign tumor.