Localization of the early-onset breast cancer gene.

In several susceptible families, it is clear that breast cancer is associated with a gene on band q21 of chromosome 17. On the basis of analogy, it seems probable that the rare germ-line gene is prototypical of a mutant form of a gene involved in the pathogenesis of the most common cancer in women. A major effort is now under way to sequence and clone this intriguing gene.