A new study of the protein-coding genes in 100 breast cancer tumors revealed vast differences among the cancers and highlights how complicated the disease really is.

"A sobering perspective on the complexity and diversity of the disease is emerging," researchers wrote in the online edition of the journal Nature, which is publishing a series of studies of the genetic changes in breast cancer.

The scientists, led by Michael Stratton at the Wellcome Trust Sanger Institute in Hinxton, England, found 73 different combinations of disease-causing mutations in the tumors, each involving up to six different genes from a set of 40 "driver genes."

Discovering that a single disease — breast cancer — can appear in so many different guises means that developing targeted therapies tailored to a patient's tumor type will remain a tall order in the near future.

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Photo: A breast cancer cell, photographed by a scanning electron microscope. (National Cancer Institute)