Abstract
Metastatic cell heterogeneity presents a significant obstacle to the development of targeted molecular and immunotherapeutics. Profiling of melanocyte differentiation antigens has revealed a nonstochastic, site-specific pattern of expression in metastases that was highest in brain, intermediate in soft tissues/lymph nodes, and lowest in visceral sites. Site-specific antigen heterogeneity, thus, is an important confounding factor to consider when assessing the potential efficacy of antigen-specific therapies.