Patterns of nodal metastases in palpable medullary thyroid carcinoma: recommendations for extent of node dissection

Abstract

Objective: To establish the frequency, pattern and location of cervical lymph node metastases from palpable medullary thyroid carcinoma (MTC). Recommendations are made regarding the extent of surgery for this tumor.

Summary background data: Medullary thyroid carcinoma is a tumor of neuroendocrine origin that does not concentrate iodine. Surgical extirpation of the thyroid tumor and cervical node metastases is the only potentially curative therapeutic option. Patterns of node metastases in the neck and guidelines for the extent of dissection for palpable MTC are not well established.

Methods: Seventy-three patients underwent thyroidectomy for palpable MTC with immediate or delayed central and bilateral functional neck dissections. The number and location of lymph node metastases in the central (levels VI and VII) and bilateral (levels II to V) nodal groups were noted and were correlated with the size and location of the primary thyroid tumor. Intraoperative assessment of nodal status by palpation and inspection by the surgeon was correlated with results of histologic examination.

Results: Patients with unilateral intrathyroid tumors had lymph node metastases in 81% of central node dissections, 81% of ipsilateral functional (levels II to V) dissections, and 44% of contralateral functional (levels II to V) dissections. In patients with bilateral intrathyroid tumors, nodal metastases were present in 78% of central node dissections, 71% of functional (levels II to V) node dissections ipsilateral to the largest intrathyroid tumor, and 49% of functional (levels II to V) node dissections contralateral to the largest thyroid tumor. The sensitivity of the surgeon's intraoperative assessment for nodal metastases was 64%, and the specificity was 71%.

Conclusion: In this series, >75% of patients with palpable MTC had associated nodal metastases, which often were not apparent to the surgeon. Routine central and bilateral functional neck dissections should be considered in all patients with palpable MTC.

Figures

Figure 1. Anatomic landmarks and lymph node compartments in the neck and upper mediastinum encountered in surgical reinterventions for MTC. Central compartment is delimited inferiorly by the innominate vein, superiorly by the hyoid bone, laterally by the carotid sheaths, and dorsally by the prevertebral fascia. It comprises lymphatic and soft tissues around the esophagus, and pretracheal and paratracheal lymph nodes that drain the thyroid bed (level VI). The submandibular nodal group (level I) is subsumed in the central compartment in some classifications. Lateral compartments span the area between the carotid sheath, the sternocleidomastoid muscle, and the trapezius muscle. The inferior border is defined by the subclavian vein, and the hypoglossal nerve determines the superior boundary. The lymph node chain adjacent to the jugular vein is divided cranially to caudally in superior jugular nodes (level II), midjugular nodes (level III), and inferior jugular nodes (level IV). Lymph nodes in the posterior triangle between the dorsolateral sternocleidomastoid muscle, the trapezius muscle, and the subclavian vein are classified as level V nodes. Mediastinal lymphatic tissue is referred to as level VII lymph nodes. (From Musholt TJ, Moley JF. Management of recurrent medullary thyroid carcinoma after total thyroidectomy. Prob Gen Surg 1997; 14:89–110, with permission)

Figure 2. Views of the neck after total thyroidectomy, parathyroidectomy, central (levels VI, VII) node dissection, and bilateral (levels II to IV) node dissections. The patient’s head is to the left and the neck contents are viewed from the right side. (A) Thyroid and central nodes have been removed. T, trachea; RCa, right carotid artery. Arrow demonstrates the right recurrent laryngeal nerve. (B) Right carotid artery and jugular vein are retracted medially. Levels III and IV nodes have been removed, and the phrenic nerve (arrow) is visible on the anterior scalene muscle. (C) Same dissection as (B), on left. LJv, left jugular vein.

Figure 3. Resected lymph nodes from a patient with multiple endocrine neoplasia type 2B. Metastatic deposits were found in level VI nodes. II, III, IV, V, VI, VII- lymph node levels in resected specimens. Level II: high jugular nodes. Level III: middle jugular nodes. Level IV: low jugular nodes. Level V: posterior triangle nodes (partial resection). Level IV: paratracheal nodes. Level VII: superior mediastinal nodes. (From Moley JF. Medullary thyroid cancer. In: Clark O, Duh Q-Y, eds. Textbook of endocrine surgery. Philadelphia: WB Saunders; 1997, with permission.)

Figure 4. Left levels III and IV nodes from a patient with sporadic MTC. A large metastatic deposit can be seen in the lower portion of the nodal group.