Schoemaker MJ, et al. - Given that previous studies suggesting a breast cancer predisposition among carriers of t(11;22)(q23;q11) have been small and had methodological shortcomings, researchers undertook a long-term prospective study of cancer and mortality risk in carriers. Sixty-five male and 101 female carriers of t(11;22)(q23;q11) who were diagnosed in cytogenetic laboratories in Britain were followed for cancer and deaths for an average of 21.4 years per subject. For cancer overall, cancer incidence was borderline significantly raised, while it increased significantly for invasive breast cancer and in situ breast cancer. Increased breast cancer risks were particularly noted at ages <50. For breast cancer, borderline significantly raised mortality was noted however, it did not rise significantly for other cancers or causes. Findings suggested several-fold increased breast cancer risk among individuals diagnosed with t(11;22)(q23;q11), with the greatest risks at premenopausal ages.