This article discusses the advances on research about cancer stem cell. Markus Frank published evidence that only a tiny subpopulation of melanoma cells has the capacity to maintain tumour progression. Frank's laboratory evidence is important for it links together cancer stem cells, disease progression and therapeutic resistance. However, Sean Morrison raised opposing evidence and suggested that as much as a quarter of all melanoma cells within any given lesion are tumorigenic. It explains that many more reseach must be done to settle the issue.