Pathological Findings in Retropharyngeal Nodes Removed during Transoral Robotic Surgery for Oropharyngeal Carcinoma

Background Retropharyngeal node (RP) metastases may be present in oropharyngeal carcinoma but are uncommon in early cancer. Transoral robotic surgery (TORS) allows for exploration and removal of retropharyngeal nodes when they are found. Pathology from retropharyngeal nodes may have prognostic significance and impact adjuvant therapy. We hypothesize that retrograde lymphatic involvement may be a factor in metastatic cancer of these nodes.

Objectives Our oropharyngeal lymph node database was utilized to identify patients who had retropharyngeal lymph nodes removed during TORS. These were compared with patients who did not have retropharyngeal nodes found.

Results Thirty-four patients out of a database of 508 patients (6.7%) in the oropharyngeal lymph node database were found to have retropharyngeal node pathology. One (n = 28), two (n = 5), or three (n = 1) nodes were removed in these patients. Nine patients of the 34 (26.5%) had cancer in the RP node basin found during retropharyngeal node dissection and one positive node was found in each of these patients. All patients had N2b or greater neck disease by the AJCC criteria. Primary site epicenter was deemed to be tonsil (n = 4), base of tongue (n = 3), and glossotonsillar sulcus (n = 2). Six patients (67%) had extracapsular spread (ECS) in the neck dissection, one patient had ECS in the RP node, but not in the neck dissection and three patients (33%) had level I metastases present. Two patients had soft tissue nodules of tumor in the retropharyngeal space that were not associated with the primary tumor but without nodal architecture present. There were no complications associated with removal of the retropharyngeal nodes during TORS.

Conclusion Retropharyngeal nodes were found in just less than 7% of patients with carcinoma of the oropharynx treated surgically, but pathological involvement by cancer in RP nodes was found in only 1.8% of all patients in the node database. Only 21.9% of all the RP nodes removed had cancer. The involvement of retropharyngeal nodes by early tongue base cancer, the high rate of AJCC pathologic stage pN2b or higher, the very strong association with level I positive nodes, and extracapsular spread in the neck all support the hypothesis that retrograde lymphatic involvement by advanced nodal disease is a risk factor for retropharyngeal node metastasis. The details of these nine patients clinical course are very informative. Nodal metastasis seen on imaging in oropharyngeal carcinoma or identified at the time of TORS can usually be removed completely. There were no complications from RP node removal, but extracapsular spread was encountered in some of the nodes in this area.