الفهرس 
Surgical Anatomy and Embryology of the Thyroid GlandOnly 14 pages are availabe for public view
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Abstract
Thyroid Carcinoma is the most common malignant disease of the endocrine system. Differentiated thyroid carcinoma (DTC) is the most common form of thyroid cancer, accounting for about 80% of all cases, and includes both papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC). Undifferentiated (Anaplastic) carcinoma accounts for 10% of cases. While other types (medullary& malignant lymphoma) account for the remaining percentage.
Exposure to radiation is the most important risk factor for thyroid cancer mostly of the papillary type. Family history and genetic alterations namely RET, Ras & P53 genes are reported in DTC.
History is usually not helpful in detecting underlying thyroid malignancy but there are well-established predictors of malignancy in thyroid nodules that include hard and fixed lesions, rapid growth of nodules, large size, associated hoarseness, dysphagia, or lymphadenopathy and a prior history of irradiation to the head or neck region.
Thyroid US is the most accurate imaging technique for the detection of thyroid nodules and this procedure is mandatory when a nodule is discovered at palpation. It can suggest malignancy by denoting certain ultrasonographic features and can guide for FNAB.
FNAB has become a gold standard in diagnosis of thyroid carcinoma especially the papillary type because of the distinctive nuclear features. The results of FNAB can be categorized as benign, malignant, indeterminate (suspicious), and nondiagnostic (unsatisfactory). An alternative to FNAB is the mini trucut biopsy.
CT is particularly useful in identifying and delineating the full extent of any cervical lymphadenopathy and the relationship of the thyroid to surrounding cervical viscera, but it is not mandatory in all cases.
An acceptable staging system in thyroid carcinoma (DTC) is the Tumor-Node-Metastasis (TNM) system taking in consideration the age of the patient because of the more aggressive behaviour of the disease in older ages others stratification. AGES, AMES & MACIS is a very considerable.
Unilateral total lobectomy may be an appropriate definitive procedure for patients with minimal thyroid cancers smaller than 1cm, which do not extend beyond the thyroid capsule and are not metastatic or angioinvasive for larger tumor with risk curteria total thyrodectomy is advisable.
In medullary carcinoma, all patients should undergo a total thyroidectomy combined with a central paratracheal neck dissection to remove all disease. This procedure is important because medullary tumors do not concentrate radioiodine, the disease is multifocal, metastases occur early, and non-surgical treatment are non effective.
Anaplastic carcinoma treatment consists of combination radiotherapy and chemotherapy. Resectable lesions are treated by total thyroidectomy and wide local excision of adjacent soft tissue. This can be followed by postoperative adjuvant chemotherapy and radiotherapy. Radiotherapy and doxorubicin are the main modalities of treatment, but invariably the tumor rapidly progresses, usually leading to death of the patient within 6 months.
Surgeons should remove all enlarged lymph nodes in the central and lateral neck areas. When enlarged nodes are identified in the lateral aspect of the neck, most surgeons perform an ipsilateral functional (modified radical neck) dissection and remove all the peri-jugular nodes from the clavicle to the hyoid, including the nodes along the spinal accessory nerve. Prophylactic lateral neck dissection is not recommended, and radical neck dissections that result in loss of function are rarely indicated for patients with PTC unless direct muscle invasion is present.
The usefulness of frozen-section diagnosis for thyroid is limited. Intra-operative frozen-section evaluation can be beneficial.
Endoscopic approaches to thyroidectomy have less pain. The only kind of thyroid cancer that may be treated with endoscopic surgery is a small differentiated carcinoma without lymph node involvement.
Most patients with differentiated (papillary or follicular) thyroid carcinoma (DTC) are treated with large activities of radioiodine (131I) after initial surgery to treat microscopic residual post-operative tumor foci and facilitate the early detection of recurrence based on serum thyroglobulin (Tg) measurement. Patients should be analyzed according to risk stratification, using scoring systems to decide whether radioiodine is indicated or not.
TSH-suppressive therapy after initial surgical treatment is another option of post surgical treatment the aiming to correct the hypothyroidism using a dosage appropriate to achieve normal blood levels of thyroid hormone and inhibit the TSH-dependent growth of residual cancer cells by decreasing the serum TSH level.
Radiotherapy and chemotherapy have limited indications in advanced cases.
In Conclusion: differentiated thyroid carcinoma (DTC) has a good prognosis. Patients considered to be low risk by the age, metastases, extent, and size (AMES) risk criteria include women younger than 50 years and men younger than 40 years without evidence of distant metastases. The 20-year survival rate may reach 98% for low-risk patients and 50% for high-risk patient.