Papillary thyroid cancer - the problem of regional lymph node metastases

Thyroid cancer is the most common malignancy of the endocrine system. With over 140,000 new cases of thyroid cancer throughout the world, it accounts for about 1% of all cancer cases. Papillary thyroid cancer (PTC) is the most common type of thyroid cancer accounting for about 85% of all thyroid cancers in iodine deficient areas. Cervical Lymph nodes (LN) are the common site of metastases in PTC. The incidence of cervical LN ranges from 20-90% of cases. Bilateral LN metastases have been observed in up to 30% of patients. Patients with lateral cervical metastases from PTC are also very likely to have clinically positive central-neck disease in up to 90%. The optimum surgical procedure concerning cervical lymph node dissection (CLND) has divided opinion of the scientific community. In the West, the surgeons mainly tend to perform selective or therapeutic CLND while in the Eastern countries like Japan an elective or routine CLND is performed. Ultrasound (US) is the preoperative imaging modality of choice used to detect cervical LN metastases and hence decide the choice of surgical procedure. However recent studies on imaging modalities have shown the sensitivity of US in the detection of metastatic cervical LN to be low between 25-60%. CT and MR are other modalities utilised, although these are not routine employed. From the few reports available in literature, the diagnostic accuracy of CT has not been established beyond proven doubt. In spite of this high incidence and the uncertain imaging for LN metastases, there is little agreement on the extent and type of cervical LND. This chapter looks at the problem of cervical LN metastases focussing on the extent and pattern, use of imaging and the surgical options available in view of evidence from literature.