Is level IIb lymph node dissection always necessary in N1b papillary thyroid carcinoma patients?

Papillary thyroid carcinoma (PTC) patients show a high rate of cervical lymphatic metastasis. However, there are no universal binding guidelines for the extent of lateral cervical lymph node dissection (LND) in such cases. In particular, the need for LND above the spinal accessory nerve (SAN) remains controversial. The present study examined whether level IIb lymph node (LN) dissection is always necessary in PTC patients with lateral cervical LN metastasis.

The study prospectively examined 167 PTC patients with lateral cervical LN metastasis who underwent modified radical neck dissection (MRND) in our institution from November 2005 to March 2007. The MRND was bilateral in 24 cases. All patients underwent level II, III, IV, and V LND. Levels IIa and IIb LNs were individually dissected in all cases. All LND was performed using strict leveling criteria by a single operating team. The patterns of lymphatic metastasis and potential risk factors for level IIb LN involvement were evaluated.

The most common site of metastasis was level III (80.6% of cases), followed by level IV (74.9%) and II (55.5%). The metastasis rates in level IIa and IIb were 55.5% and 6.8%, respectively; all level IIb LN metastasis was accompanied by level IIa metastasis (p=0.001). In addition, level IIb LN metastasis was found to be associated with the aggressiveness of lymphatic metastasis (i.e., the total number of metastatic LNs) (p<0.0001).

A level IIb LND should be performed when there is clinical or radiological evidence of lymphatic metastasis. In the absence of such evidence, the findings suggest that level IIb LND is not necessary in N1b PTC patients when there is no level IIa LN metastasis, or when the metastasis is not aggressive.