Thyroid Nodules and Thyroid Cancer

A thyroid nodule is a discrete lesion within the thyroid gland. Nodules are common, and most are benign. The clinical task is not to find every small lesion; it is to identify the relatively few lesions that need treatment while avoiding unnecessary biopsy, surgery, and lifelong thyroid hormone replacement. Many nodules are found incidentally during imaging performed for another reason. This matters because detecting a lesion is not the same as improving health. Canadian thyroid cancer incidence rose sharply as ultrasound use increased, while mortality remained relatively stable—a pattern consistent with overdiagnosis of small, indolent papillary cancers. Thyroid cancers differ substantially in biology: - Differentiated thyroid cancer (DTC) includes papillary and follicular cancers. These tumours arise from follicular cells and often retain iodine uptake and thyroglobulin production. That biology permits radioiodine treatment in selected cases and makes thyroglobulin useful for follow-up. - Medullary thyroid carcinoma (MTC) arises from parafollicular C cells. It produces calcitonin rather than thyroglobulin and may be hereditary through a germline RET mutation. - Anaplastic thyroid carcinoma (ATC) is undifferentiated, aggressive, and often rapidly compresses the trachea....