Tumour of the thyroid that arises from the parafollicular C-cells, which secrete calcitonin.
Approximately one-third are seen in children and young adults as part of MEN (multiple endocrine neoplasia) type II syndrome. The other two-thirds are sporadic cases.
The parafollicular cells originate from neural crest tissue during embryonic life, but merge with the embryonic thyroid and are dispersed amongst the follicular cells. Parafollicular cells normally secrete calcitonin, a polypeptide, in response to small increases in calcium. The tumour cells secrete calcitonin and carcinoembryonic antigen (CEA) and are also capable of secreting prostaglandins and serotonin.
One or both thyroid lobes are enlarged and firm. Cervical lymph nodes are palpable in about half of cases, but the tumour is generally slow growing and tends only to metastasise to local lymph nodes. Those associated with MEN syndrome tend to be more aggressive.
The tumour is composed of sheets of small cells containing neuroendocrine granules with a hyaline stroma between them. Spread is mainly to local lymph nodes.
Calcitonin levels are raised, although serum calcium levels are normal. Calcitonin is also used for followup and for screening of relatives.
Total thyroidectomy and dissection of lymph nodes in the central neck compartment.