'Metastasis, particularly to visceral organs, such as the lung, accounts for the majority of breast-cancer related mortality,' says the study's lead author.

The findings shed new light on the biology of breast-cancer metastasis, and could lead to a possible prognostic tool and new targets for treatment, say the researchers at Memorial Sloan-Kettering Cancer Center (MSKCC) who identified the gene set.

"Our work shows that the ability of a tumor to form metastases depends on the combined action of multiple genes -- and a different set of genes is required for each organ the tumor spreads to," said Joan Massagu