The most specific investigations regarding the diagnosis of cancer metastasis is imaging. Many imaging modalities are available including X-rays, which can be used routinely and can show some cancer metastases especially those who are dense enough and those who affect bones.
CT scan: It is a better imaging tool at showing metastases and provide a more accurate localization of the metastases, it can also be used with a contrast dye to enhance its visualization.
MRI scan: It is also a good imaging modality to diagnose metastasis in some types of cancer especially those of the brain and spinal cord.
PET scan: It can also be used. It detects cancer metastases across the whole body by measuring the metabolic activity of cells. Cancer cells consume substances at a much higher rate than normal cells and can therefore appear on PET scan.
Scintigraphy: Scintigraphy is a somehow outdated technique that involves a radioactive isotope into the blood stream, then taking an image of the suspicious site to reveal the presence of metastases. It has largely been replaced and its only current use is in thyroid cancer.