Surprisingly, biallelic mutations in the BRCA2 breast-cancer-susceptibility gene 
were found in Fanconi anemia (FA), a rare hereditary disorder characterized by 
chromosomal instability, hypersensitivity to DNA cross-linking agents, and 
cancer susceptibility. This suggests that a defect in the FA pathway might 
predispose to familial breast cancer. A previously reported molecular 
interaction between BRCA1 and the FA protein, FANCD2, supports the hypothesis 
that both breast-cancer-susceptibility genes are components of the FA pathway, 
functioning in DNA-damage response. However, an alternative hypothesis, that 
group FA-D1 with mutated BRCA2 represents a FA-like syndrome that is involved in 
a pathway distinct from the FA pathway, cannot be excluded. Similar syndromes 
would also be expected when recombination genes, such as Rad51 and its paralogs, 
are mutated.