Introduction:

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine malignant tumor derived from the parafollicular cells or thyroid C cells. At the time of diagnosis, over 50 % of patients have lymph node metastases, and 10 % have distant metastases. Prognosis is largely dependent on tumor stage and, therefore, early diagnosis is essential.

Objective:

The aim of this work is to present an updated review of the diagnostic approach for MTC.

Summary:

Thyroid ultrasound is the main tool used for thyroid nodule stratification; however, most studies have focused on papillary thyroid carcinoma. In MTC, ultrasonographic findings suggestive of malignancy are usually less frequent and this could delay diagnosis and treatment. Therefore, ultrasound examination should be combined with additional diagnostic techniques. The sensitivity of the fine-needle aspiration cytology is generally low for these types of tumors and when MTC is suspected, it is recommended to perform immunohistochemical for calcitonin and measurement of calcitonin in washout fluid of thyroid nodule aspirate. Serum calcitonin is the most sensitive marker for diagnosing this condition; however, its routine measurement in the evaluation of thyroid nodule is controversial. Serum calcitonin levels are related to C-cell mass and the presence of lymph node metastases. When these levels are above 500 pg/mL suggest distant metastatic disease and additional imaging procedures are indicated. Genetic testing should be offered to all patients because 25 % of these carcinomas are hereditary and are part of multiple endocrine neoplasia type 2 syndrome associated with a germline RET mutation.

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