Surgery is the primary treatment for MTC. There is a general consensus that those patients who present with clinically evident MTC should have total thy-roidectomy with cervical node clearance.34 Total thy-roidectomy is necessary regardless of the size of the tumor because MTC is often bilateral and multifocal. Patients with gross lymphadenopathy should have a
Table 3-2. PROGNOSTIC FACTORS IN MEDULLARY THYROID CANCER
Clinical Pathologic Biochemical/Molecular
Age Stage (TNM) Elevated serum CT/CEA
Gender Tumor size DNA ploidy
Diarrhea* Nodal metastasis Amyloid IHC
Bone pain* Distant metastasis CT/CRGP IHC
Extrathyroidal invasion Somatostatin IHC
Thyroiditis N-myc expression
'Usually indicates the presence of distant metastasis.
CEA = carcinoembryonic antigen; CGRP = calcitonin gene-related peptide; CT = calcitonin; DNA = deoxyribonucleic acid; IHC = immunohistochemistry;TNM = tumor, node, metastasis.
bilateral modified radical functional neck dissection, preserving the spinal accessory nerve, internal jugular vein, sternocleidomastoid muscle, and cervical sensory nerves. Even if no gross lymphadenopathy is detected at the time of initial thyroidectomy, at least a central cervical node clearance should be done because up to 75% of these patients with MTC have cervical node metastasis to the central neck compartment. In addition, the presence of MTC lymph node metastasis cannot be determined accurately intraop-eratively. Furthermore, the presence of cervical node metastases is associated with an increased risk of recurrence and mortality (especially the presence of > 10 positive nodes, lymph node size > 1 cm, and involvement of more than 2 cervical lymph node compartments).1035 Central neck node dissection (level VI) should consist of removal of all lymph nodes and fibrofatty tissue from the hyoid bone (superiorly) to the carotid sheaths (bilaterally) and innominate vessels (inferiorly) (see Figure 3-9). In a functional modified radical neck dissection, all nodal and fibrofatty tissue should be removed from the trapezius muscle (posterolaterally), clavicle, and upper mediastinum (inferiorly) and up to the mandible (superiorly) (see Figure 3-8).
In patients diagnosed by screening to be at risk of developing MTC (asymptomatic MTC), a prophylactic total thyroidectomy is recommended. There is a general consensus that children older than 6 years should have preventive total thyroidectomy.9,36 Some experts, however, perform prophylactic thyroidec-tomy in children as young as 1 year old, whereas others follow these patients until they develop basal or stimulated hypercalcitoninemia. The need for prophylactic central neck node dissection has not yet been clearly established; some surgeons recommend prophylactic central neck dissection in children older than 10 years, whereas some routinely perform central neck node dissection at the time of total thy-roidectomy.36 In 139 patients who had prophylactic total thyroidectomy with at least a central neck node dissection for a positive screening test for MTC, 8.6% had regional lymph node metastasis.9 Central neck node dissection at the time of prophylactic total thyroidectomy is recommended if (1) there is an intrathyroidal lesion at the time of surgery or on pre-operative ultrasonography, (2) the basal or stimu lated calcitonin level is elevated, or (3) there is obvious lymphadenopathy present.9
The need for parathyroidectomy at the time of total thyroidectomy and cervical lymph node clearance is controversial in patients with MTC diagnosed by screening or who are symptomatic. Some experts recommend removal of all parathyroid glands at the time of thyroidectomy and autotransplantation. The rationale for this management strategy is that some surgeons do not believe that an adequate total thyroidectomy and cervical lymph node clearance can be done without devascularizing the parathyroid glands. In our experience, however, the parathyroid glands can usually be left in situ without limiting a complete cervical neck node clearance and minimizing the risk of hypoparathyroidism. In situations in which the viability of a parathyroid gland(s) is questionable, parathyroid autotransplantation to the forearm in patients with MEN type IIA and to the sternocleidomastoid muscle in patients with sporadic MTC, familial MTC, and MEN type IIB is recommended. The remaining parathyroid tissue should be cryopreserved.
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