What defines a useful marker of metastasis in human

In this issue of the Journal, O’Connell et al. (1) describe the identification of a region on the long arm of chromosome 14 that is apparently involved in the progression of breast cancer toward metastasis. Measuring loss of heterozygosity, the investigators found that the majority of lymph node-negative breast tumors did not amplify a region linked to D14S62 and D14S51, while lymph node-positive breast tumors retained heterozygosity for these same markers. These data could imply the existence of a metastasis-promoting gene. Alternatively, the observed molecu-lar changes may be a marker of metastatic propensity. Since metastasis is the most lethal attribute of a cancer, it is critical that tumors be diagnosed while still localized to achieve the highest probability of long-term survival and quality of life. In the absence of objective evidence that metastases do not exist, earlier diagnosis would accomplish three things: 1) increase th