Thyroid cancer

Thyroid cancers account for less than 1% of all malignancies but are much the most frequent cancers of endocrine organs.

Follicular epithelial cell cancer—the commonest type; may be induced by exposure to radiation; can be highly undifferentiated or differentiate into recognizable follicular cells, sometimes with retention of hormone biosynthesis; typically present with an asymptomatic thyroid nodule; usually diagnosed by fine needle aspiration biopsy; treatment is typically by total or near total thyroidectomy, with radio-iodine then administered to remove any remaining thyroid tissue (followed by long-term thyroid replacement therapy).

Medullary thyroid carcinoma—arises from parafollicular C cells; comprise 5 to 10% of all thyroid cancers; hereditary autosomal dominant forms associated with germ-line point mutations in the RET proto-oncogene occur as part of multiple endocrine neoplasia (MEN) type 2A or 2B, or as isolated familial medullary carcinoma; typically present with a solitary thyroid nodule, accompanied in 50% of cases by cervical lymphadenopathy; can be associated with unusual hormonal effects, including secretory diarrhoea; diagnosis often made by fine needle aspiration biopsy, also by finding raised serum calcitonin; treatment is by total thyroidectomy, followed by monitoring of serum calcitonin levels (and long-term thyroid replacement therapy); testing for the presence of RET mutations (see Chapter 13.10) allows family testing, with prophylactic thyroidectomy recommended for affected individuals.

Rare thyroid tumours—include (1) anaplastic carcinomas—present as a rapidly enlarging and fixed thyroid mass, sometimes with local pain; rapidly fatal; (2) sarcomas; and (3) primary lymphomas— usually present as a rapidly enlarging thyroid mass in a patient with Hashimoto’s thyroiditis.