Management of metastatic lymph nodes in thyroid cancer

Abstract

The thyroid gland is not uncommon site of cancer. It represents the most common site of malignancy of endocrine system. The incidence of thyroid carcinoma has increased in recent years. Diagnosis was facilitated by two important developments: the widespread use of improved imaging techniques and the popularity of fine-needle aspiration biopsy. In National Cancer Institute of Egypt the incidence of cancer thyroid was: 2.1%, 2.3% and 1.95% at 2002, 2003 and 2004 respectively. Thyroid Cancer occurs primarily in young and middle aged adults with mean age at diagnosis around the mid 40’s for the papillary type, 50’s for the follicular type. Thyroid Cancer is two to four folds more frequent in females then males. The most common thyroid neoplasms are papillary carcinoma (50–80% of the total), followed by follicular carcinoma (10–40%). Thyroid cancer typically presents clinically with a palpable thyroid nodule. Laboratory investigations include thyroid function tests (serum TSH, T3 and T4). Imaging studies include cervical ultrasonography, thyroid scan, computed tomography (CT) and positron emission tomography (PET CT) of the neck. Fine needle aspiration cytology of discrete neck swellings remains the mainstay of diagnosis of thyroid cancer Lymph node metastases of differentiated thyroid cancer (DTC) occur at a higher rate than is often appreciated and are often in unpredictable sites. About 60% of patients with PTC had cervical lymph node metastases: one third was bilateral and almost 25% were in the contralateral para-tracheal area. Cervical lymph node micro-metastases are often found at sites that bear little relation to the site of the thyroid tumor, especially in patients with micro-carcinoma. Lymph node metastases can be identified by performing a careful neck ultrasonography before surgery. The majority of patients with DTC have papillary carcinoma and most are treated by total thyroidectomy. Metastases to the regional cervical lymph nodes are relatively common and occur early. The incidence of palpable neck metastases in papillary carcinoma is between 15% and 40%, and up to 90% have occult disease. In the untreated neck, patterns of lymph node drainage occur in a recognized and systematic manner, which facilitates selective neck surgery. Lymph node metastases occur commonly in levels III, IV,VB, VI, and VII. In the N0 neck in level VI, routine dissection should be considered as part of a total thyroidectomy in high risk patients. There is no role for routine elective surgery for lateral neck compartment in the N0. When there is palpable (or suspected) disease within the lateral neck compartment, a selective neck dissection should be carried out including at least levels III, IV, and VB preserving wherever possible, the sternomastoid muscle, accessory nerve, and internal jugular vein. Selective neck surgery for differentiated thyroid cancer can be performed with low morbidity. There is no role for “berry picking”. Follow-up should be for life.