الفهرس 
Anatomy and Embryology of thyroid glandOnly 14 pages are availabe for public view
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Abstract
Microscopic regional lymph node metastases of papillary cancer occur in up to 80 percent of patients. However, only about 35 percent have cervical or mediastinal node metastases that are detected at the time of initial surgery. Because microscopic nodal disease is rarely of clinical importance or subsequent radioiodine administration ablates these occult foci, and observational studies have not shown a clear benefit in reducing locoregional recurrence rates, many authors argue that prophylactic central neck dissection of microscopic lymph node metastases that are not clinically identifiable at the time of surgery may not improve long-term outcome and could subject patients to more risk than benefit. (Shan, Cheng‐Xiang, et al.2012). Central neck dissection can be either unilateral or bilateral and can be done either therapeutically or electively. A therapeutic central compartment neck dissection is performed when the nodal metastasis is clinically apparent (clinically N1a), whereas an elective central compartment dissection is prophylactic for nodal metastasis that is not detected clinically or radiologically (clinically N0). Excision of central cervical lymph nodes that are neither clinically nor radiographically suspicious for malignancy (prophylactic central cervical lymphadenectomy) may also decrease recurrence rates and improve disease-specific survival for some types of thyroid cancer. (White, Matthew L., Paul G. Gauger, and Gerard M. Doherty. 2007). Prophylactic central neck dissection for papillary thyroid cancer remains controversial. Although small foci of clinically and radiographically undetectable level VI nodal metastasis are common among papillary thyroid cancer patients (occurring in up to 50% of cases), it remains unclear which proportion of these micrometastases will become clinically significant. The benefits and harms of prophylactic central neck dissection for well-differentiated thyroid cancer has not been reported. Thus, whether or not to perform prophylactic central neck dissection in the setting of papillary thyroid carcinoma remains at the discretion of the operating surgeon. This standard is formally supported by the recommendation of the American Thyroid Association, which states that “prophylactic central-compartment neck dissection (ipsilateral or bilateral) may be performed in patients with papillary thyroid carcinoma with clinically uninvolved central neck lymph nodes (Cranshaw, Isaac M., and Bruno Carnaille.2008). Complication of prophylactic central neck dissection may include, Bilateral RLN injury, potentially resulting in airway compromise, is quite unusual. Resection and/or devascularization of the parathyroid glands can result in permanent or transient hypocalcemia. The risk of injury to the RLNs and parathyroid glands increases in reoperative cases, especially when these are performed by inexperienced surgeons. When considering the pros and cons of this procedure, one must ask first why it should not be done. In many of the papers that have advocated routine central compartment dissection, comments that this should be restricted to patients whose treating teams ‘have available surgical expertise’ or restricted to those ‘with experienced hands’ are made. There is no controversy that all clinically apparent nodal disease should be removed at initial operation via a compartmentoriented approach; thus, a therapeutic central neck dissection is almost always indicated at time of thyroidectomy in the presence of clinically detectable nodal disease. The indications for elective central neck dissection are relative and more controversial. In general they include (1) Accurate pathologic staging for selective postoperative use of radioiodine in low-risk primary tumors. (2) Prophylactic node dissection in high-risk primary tumors in hopes of reducing recurrence and subsequent morbidity from reoperation. Prophylactic central lymph node dissection must be applied in light of available surgical expertise and must balance the risks of the disease and its treatment with any benefit to the patient. Though central lymph node dissection may be associated with higher morbidity, reoperative surgery is potentially more challenging, creating the possibility of further complications. Additionally, lymphadenectomy may also more clearly stage patients and define who may benefit from adjuvant therapy. (Amanda M. Laird, David L. Steward, Gerard M. Doherty. 2012).