Assuming that IFNγ exerts a strong selective pressure on tumour cells we screened an ‘in-house' collection of short-term cultured melanoma cell lines for mutations in genes of the IFNγ signalling pathway and detected JAK1, JAK2 and STAT1 alterations in cells and corresponding tumour tissue from 6 out of 47 patients. The gene discussed is JAK2; the disease is melanoma.