Thyroid cancer. Light micrograph of a section through a thyroid gland with papillary adenocarcinoma (right side of image), the most common form of thyroid cancer. Adenocarcinomas are cancers that arise from glandular tissue. The cause of thyroid cancer is not known. It is more common in women than men. Symptoms can include swelling in the neck and difficulty swallowing or breathing. Treatment is with the surgical removal of the tumour or gland, often combined with radioactive iodine therapy. Normal thyroid is to the left of the image. Magnification: x100 when printed at 10 centimetres wide. Human tissue.