Thyroid cancer. Coloured Gamma Camera scan (scintigram) of the human thyroid gland in the neck, showing cancer. The thyroid gland consists of two joined lobes, as seen here, situated on either side of the trachea (windpipe). A cancerous tumour has formed in the lobe at left (blue), destroying tissue and affecting the blood supply. Thyroid cancer may grow rapidly, pressing on the voice box and spreading to lymph nodes. It is one of the cancers associated with exposure to radioactive fallout. Gamma scanning uses a radio- active tracer (here, Technetium-99m) injected into the blood and detected by a gamma camera.