PATTERNS OF
LYMPH NODE METASTASES IN MEDULLARY THYROID CANCER-CLINICAL IMPLICATIONS
Medullary
thyroid cancer (MTC) has a more aggressive biological behavior compared to the
more common differentiated (papillary and follicular) thyroid cancer. Lymph
node metastases are common among patients with MTC (~ 75 % at the time of
surgery). Surgery remains the only potentially curative therapeutic method in
the management of MTC. In order to achieve cure, total thyroidectomy is inadequate
and should be almost always be combined with neck lymph node dissection. Knowledge
of the pattern of lymph node metastases in MTC is of crucial importance for the
practicing endocrine surgeon, in order to achieve radical resection of the
disease at the time of initial surgery.
The pattern
of lymph node metastases, as demonstrated for papillary thyroid cancer (PTC),
may also apply to MTC; however, the size and location of the primary tumor are
significant parameters in predicting the location of involved lymph nodes. For
example, tumors located in the upper thyroid pole metastasize first to the
upper portion of the ipsilateral lateral compartment (levels II or III), whereas
MTCs in the middle and lower portions of the gland spread first to the central
compartment (level VI). MTCs in the upper pole of the thyroid, involving the
lateral compartment nodes on the ipsilateral side, skip the central compartment
in a significant percentage of patients (~ 25 %).
The number
of the involved lymph nodes in the central compartment has prognostic significance
in predicting the risk for the presence of metastatic disease in the lymph
nodes of the ipsilateral and contralateral lateral compartment. In one study of
195 patients with MTC, the rate of ipsilateral lateral compartment lymph node
metastases was 10 %, 77 % and 98 % when the number of involved central compartment
lymph nodes was 0, 1 – 3 or ≥ 4. The rate of contralateral compartment
lymph node metastases was 5 %, 38 % or 77 % when the number of involved lymph
nodes in the central compartment was 0, 1 – 9 or ≥ 10.
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