Thyroid cancer. Coloured transmission electron micrograph (TEM) of a section through a thyroid gland with follicular carcinoma a form of thyroid cancer. Malignant follicular epithelial cells surround pink colloid. (top right). Follicular thyroid carcinoma (FTC) is the second most common cancer of the thyroid, after papillary carcinoma. Follicular and papillary thyroid cancers are considered to be differentiated thyroid cancers; together they make up 95% of thyroid cancer cases. For follicular thyroid cancer surgery, by far, is the most common first treatment. Human tissue. Magnification: x1600 when printed at 10 centimetres across.