[Rare metastases]

The paper reports a number of cases of uncommon metastasis confirmed by histological tests in surgical biopsies; following a brief discussion of the literature on this topic and in particular on the basis of an earlier study by one of the authors, the paper affirms that metastasis is related to general and local biological factors, that the diffusion of neoplastic cells is an early and generalised phenomenon opposed by organic defence mechanisms, and that the concept of uncommon metastasis should be revised, without resorting to fixed anatomical references, according to a general "impregnation" of tumour cells.