Tumour embolism. Light micrograph of a section through an embolism (blood clot) caused by cells from a cervical cancer. The cells have left the primary tumour and are metastasising (spreading) around the body. If the embolism completely blocks an artery it can lead to tissue death, which can be fatal if it occurs in the lung (pulmonary embolism), heart (heart attack) or brain (stroke).