Metastatic Thyroid Cancers : Introduction
Introduction: Papillary thyroid carcinoma (PTC), which accounts for about 90% of all thyroid cancers, has a tendency to invade the lymphatics readily. This can create multiple tumor nodules within the thyroid gland as well as frequent metastases to cervical lymph nodes (shown in this image). The prevalence of nodal metastases in PTC has previously been reported to be between 35% to 55% in various studies. Currently, with high-resolution imaging, extensive neck dissection, and careful histologic evaluation, cervical lymph node metastases can be identified in almost 80% of PTC. PTC can also involve mediastinal lymph nodes in about 5% of cases. Other Thyroid Cancers: Follicular thyroid carcinoma (FTC) tends to spread via blood-borne route rather than via lymphatics. Nodal metastases in FTC are virtually unknown and invariably turn out to be follicular variant of papillary thyroid carcinoma. Hurthle cell carcinoma can invade lymphatics and spread to regional lymph nodes. Lymph node metastases occur quite commonly in poorly-differentiated and undifferentiated thyroid carcinomas. Almost 70% of patients with medullary thyroid carcinoma who present with a thyroid mass have metastases to cervical lymph nodes.