Metastasis, or metastatic disease, is the spread of a cancer or other disease from one organ or part to another not directly connected with it. The new occurrences of disease thus generated are referred to as metastases /mə ˈtæs tə siːz/ (sometimes abbreviated "mets"). It was previously thought that only malignant tumor cells and infections have the capacity to metastasize (also spelled metastasise); new research has caused this to be reconsidered.