Metastatic prostate cancer. Coloured gamma camera scan (scintigram) of the pelvis of a patient suffering from metastatic prostate cancer. Metastasis is the growth of secondary malignant tumours from a primary cancer. The primary cancer is seen as a large yellow growth at the prostate gland (at centre). Tumorous growth is seen to have spread to the head of the femur (thigh bone, at right). The prostate is a male sex gland which secretes a fluid part of semen. Prostate cancer usually affects elderly men. Scintigrams are made by injecting the patient with a radioactive tracer (Technetium-99m) which accumulates in cancerous growths and is visualised by gamma camera.