Medullary carcinoma - Malignant tumours of the thyroid

Medullary carcinoma

Definition

Tumour of the thyroid that arises from the parafollicular C-cells, which secrete calcitonin.

Aetiology

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.

Pathophysiology

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.

Clinical features

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.

Microscopy

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.

Investigations

Calcitonin levels are raised, although serum calcium levels are normal. Calcitonin is also used for followup and for screening of relatives.

Management

Total thyroidectomy and dissection of lymph nodes in the central neck compartment.