In recent years doctors have turned to a new treatment for cancer, immunotherapy, which works by leveraging the body's own immune system to fight tumours.

The technique has largely focused on white blood cells called T-cells, which are "trained" to recognise and attack cancer cells.

But the innovative treatment only works well for around 20 percent of patients, and researchers have been trying to understand why some people respond better than others.

Three papers published on Thursday in the journal Nature point the way, identifying a key formation inside some tumours: tertiary lymphoid structures (TLS).