The first step towards choosing the best lung cancer treatment is to figure out what specific kind of lung cancer a patient has. Usually, doctors can determine cancer type by surgically removing part of a tumor and examining the appearance of tumor cells under a microscope. But sometimes tumor samples are damaged and difficult to analyze visually, so a second method would be useful to help confirm a diagnosis. Researchers have now developed a new test that can determine which genes are turned on or off in tumor cells, allowing them to distinguish between the most common types of lung cancer (adenocarcinoma, carcinoid, small cell carcinoma, squamous cell carcinoma). Samples of tumors are already routinely collected, and, in an experiment, examining them and analyzing their genetics was found to be a viable predictor of a tumor’s microscopic appearance. Researchers hope that their test will bring more accurate diagnoses to doctors and patients, which in turn could lead to better treatment recommendations and better outcomes.