The present invention relates to mutations in Epidermal Growth Factor Receptor (EGFR) and methods of detecting such mutations as well as prognostic methods method for identifying a tumors that are susceptible to anticancer therapy such as chemotherapy and/or kinase inhibitor treatment. The methods involve determining the presence of a mutated EGFR gene or mutated EGFR protein in a tumor sample whereby the presence of a mutated EGFR gene or protein indicates the tumor is susceptible to treatment.