medullary carcinoma of thyroid

(redirected from atypical carcinoma of thyroid)

medullary carcinoma of thyroid

a malignant thyroid neoplasm composed of calcitonin producing C-cells and amyloid rich stroma; it may be sporadic or familial; the familial form may be part of the multiple endocrine neoplasia syndrome, type 2A and 2B.

medullary carcinoma of thyroid

A neuroendocrine tumour that comprises ±5% of thyroid cancers, arising in the C (parafollicular) cells of the ultimobranchial cleft—i.e., neural crest origin. It is either sporadic (70–90% of cases) or inherited (10–30%) as part of the autosomal dominant multiple endocrine neoplasia (MEN) types 2A or 2B, the latter in association with mutations of the RET proto-oncogene. The average age at diagnosis is 50; it is slightly more common in women.

Clinical findings
Related to local growth and compromised of regional structures; increased calcitonin causes hypercalcaemia, hypertension, paraneoplastic syndromes (e.g., Cushing syndrome) and neuromas.

Clinical forms
• Sporadic—70–90% of cases, mean age of onset 45; presenting as a solitary “cold nodule” (by thyroid scan), which may be accompanied by intractable diarrhoea and Cushing’s syndrome. 
• Familial—10–30% of cases, mean age of onset 35; multifocal and bilateral, accompanied by C-cell hyperplasia of residual thyroid tissue; familial MCT is often autosomal dominant and associated with multiple endocrine adenomatosis, usually type II (which has a germline abnormality on chromosome 10, an earlier age of onset and is often bilateral) or occasionally type III (IIb; less common, but more aggressive and rarely a non-aggressive form of MCT that is not associated with other neural or endocrine lesion).

Lab
MCTs may produce ACTH-like substance, biogenic amines, CEA, corticotropin-releasing factor, NGF, prolactin-releasing hormone, prostaglandins, melanin-stimulating hormone, histaminase, beta-endorphin, 5-hydroxytryptamine, serotonin, somatostatin, thyroglobulin.

Thyroid function tests
Usually normal.

Risk factors
Family history of multiple endocrine neoplasia MEN 2A or 2B, history of phaeochromocytoma, mucosal neuromas, hyperparathyroidism; RT to head or neck, the risk of radiation-induced thyroid nodularity and carcinoma increases with radiation dose and decreases the older the person was at the time of irradiation.
 
Metastases to
Cervical lymph nodes, mediastinum, lungs, liver, bone, brain, adrenal glands.

Management
Total thyroidectomy, radioiodine.
 
Prognosis
70–80% 5-year survival; sporadic MCT has a 50% 10-year survival; 10- and 20-year survival is 63% and 44% respectively (papillary thyroid carcinoma has 95% 10-year survival). 70% develop nodal metastasis.

medullary carcinoma of thyroid

Atypical carcinoma, compact small cell carcinoma, solid carcinoma, of thyroid A tumor comprising 3-10% of thyroid CAs, arising in the C–parafollicular–cells of ultimobranchial cleft–neural crest origin Clinical Tumors metastasize to cervical lymph nodes, mediastinum, lungs, liver, bone, adrenal glands; ↑ calcitonin causes hypercalcemia, HTN, paraneoplastic syndromes–eg, Cushing syndrome and neuromas; MCTs may produce ACTH-like substance, biogenic amines, CEA, corticotropin-releasing factor, NGF, prolactin-releasing hormone, PGs, melanin-stimulating hormone, histaminase, β-endorphin, 5-hydroxytryptamine, serotonin, somatostatin, thyroglobulin Risk factors RT to head or neck, family Hx of multiple endocrine neoplasia, Hx of pheochromocytoma, mucosal neuromas, hyperparathyroidism Treatment Total thyroidectomy Prognosis 70-80% 5-yr survival; sporadic MCT has a 50% 10-yr mortality–10- and 20-yr survival is 63% and 44% respectively; in contrast, papillary thyroid carcinoma has 95% 5- and 10-yr survival. See Anaplastic carcinoma of thyroid, Follicular tumor of thyroid, Papillary carcinoma of thyroid, Thyroid lymphoma.
Medullary carcinoma of thyroid–clinical forms
Sporadic MCT 80-90% of cases, mean age of onset 45, presenting as a solitary 'cold'–by thyroid scan–nodule variably accompanied by intractable diarrhea and Cushing's syndrome
Familial MCT 10-20% of cases–in one study with ≈ 23.5 years follow-up 11% were familial, mean age of onset 35, presenting as a multifocal and bilateral mass, accompanied by C-cell hyperplasia of residual thyroid tissue; familial MCT is often AD and associated with multiple endocrine adenomatosis, usually type II–which has a germline abnormality on chromosome 10, an earlier age of onset, and is often bilateral, or occasionally type III–IIb, less common, but more aggressive and rarely a non-aggressive form of MCT that is not associated with other neural or endocrine lesions

med·ul·lar·y car·ci·no·ma of thy·roid

(med'ŭ-lar'ē kahr'si-nō'mă thī'royd)
A malignant thyroid neoplasm composed of calcitonin producing C-cells and amyloid rich stroma; it may be sporadic or familial; the familial form may be part of the multiple endocrine neoplasia syndrome, types 2A and 2B.
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