Australian scientists have discovered that special immune cells have the power to put melanoma tumours "to sleep", potentially paving the way for new treatments. The cancer cells aren't completely killed. They are still there, but they are held in check by the tissue-resident memory T cells. It seems that the T cells can patrol the skin and watch over the melanoma tumour cells. Melanoma remains the fourth most commonly diagnosed cancer in Australia, behind breast cancer, prostate cancer and colorectal cancer. Australia and New Zealand have the world's highest incidence rate for melanoma.