Cancer rarely stays in the same place, which makes fighting it extremely tricky. Tumour cells can spread to other parts of the body via the lymph system - a complicated network of vessels and nodes. The patient pictured has head and neck cancer (largest yellow blob near mouth is a tumour). The smaller blobs are sentinel lymph nodes – the first nodes any cells from the tumour are likely to reach. The sentinel nodes have been identified using SPECT imaging, which works by tracking a radioactive substance through the lymph system. The tracer is injected near the tumour, and emits gamma rays, which are detected by a special camera. When the tracer drains into lymph nodes the bright hotspots result. These nodes must now be removed by a surgeon and tested for tumour cells, so doctors know what stage the cancer is at, and where to target treatment.
Written by Emma Stoye
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.