Insignificance of prophylactic upper mediastinal lymph node dissection by sternotomy for papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is characterized by extensive lymph node metastases. A considerably high frequency of lymph node metastases in the upper mediastinal compartment (UMC) has been reported. However, the significance of prophylactic upper mediastinal lymph node dissection (UMLND) by sternotomy as an appropriate therapeutic option has not yet been clarified. Thirty-three patients who underwent prophylactic UMLND by sternotomy for PTC at our institution between 1980 and 1987 (group A) were analyzed. One hundred and fifty-one consecutive patients with PTC who underwent curative total thyroidectomy, bilateral modified radical neck dissection, and UMLND by collar incision as initial treatment between 1990 and 1999 (group B) were analyzed as controls. The patterns of lymph node metastases in the cervical compartment of these two groups were comparable; distribution of lymph node metastases in UMC was considerably less frequent than in other compartments. Clinical relapse in UMC was not observed in both groups. No significant difference in disease specific survival or relapse free survival between group A and B was observed. The lack of clinical relapse in UMC in group B indicates that most of the lymph node metastases in this compartment could be resected by the conventional collar incision or most microscopic lymphatic metastases could remain dormant as with lateral microscopic node metastases. Thus, upper mediastinal lymph node metastases requiring sternotomy to resect in curable patients with PTC could be less frequent. Prophylactic UMLND by sternotomy for PTC is discouraged from a clinical view point.