Primary tumour

The primary defines the cancer's biology, its likely drivers and its treatment, because the spread cells (metastases or secondaries) inherit its identity; a pathologist can usually recognise the origin from the cells' appearance and markers. Local treatments, surgery and radiotherapy, are aimed at the primary and can cure a cancer that has not spread; once distant metastases exist, removing the primary usually no longer cures, though it may still relieve symptoms. In about two percent of cases, the primary is never found (cancer of unknown primary), and genomic profiling is increasingly used to infer where it came from.