Consistent with its role as a classical tumor suppressor gene, loss of heterozygosity (LOH) or “second-hit” somatic mutations in the inherited wild-type NF1 allele have been detected in a variety of tumors in patients with NF1, including pheochromocytomas [50], breast cancer [51], and hematologic malignancies [52]. This evidence concerns the gene NF1 and breast cancer.