Medullary thyroid carcinoma: role of high-resolution US.

Medullary thyroid carcinoma accounts for 10% of thyroid malignancies. Accurate determination of the extent of disease is important because surgery is required for initial treatment and recurrence. High-resolution (10-MHz) ultrasonography (US) of the neck was used to study 15 patients with medullary thyroid carcinoma; nine of the 15 had undergone thyroidectomy but had biochemical evidence of tumor recurrence. Metastatic cervical lymph nodes were detected with US in all 12 patients who had metastatic nodes at surgery, although these nodes were palpable in only four. Punctate bright echogenic foci were seen within some of the nodes in nine of the 12 patients (75%). Similar bright echogenic foci were seen within the primary intrathyroid tumor in five of the six patients who had not yet undergone thyroidectomy (83%). Pathologically, these foci correlated with deposits of calcium surrounded by amyloid, which is characteristic of medullary thyroid carcinoma. US is useful for the detection of nonpalpable recurrence of cervical metastatic lymph nodes, and because it is noninvasive and relatively inexpensive, it should be the first imaging investigation performed after thyroidectomy.