[Retropharyngeal node metastasis in cancer of the oropharynx and hypopharynx: analysis of retropharyngeal node dissection regarding preoperative radiographic diagnosis].

In our department, all patients with advanced carcinoma of the oropharynx and hypopharynx are treated by retropharyngeal (RP) node dissection in addition to primary resection and standard neck dissection. Records of 42 patients (11 oropharynx, 29 hypopharynx and 2 retromandibula) who received RP node dissection from 1992 to 1996 in our department were examined for metastasis to RP nodes and for preoperative radiographic diagnosis (MRI or CT). The criteria for radiographic involvement of RP nodes are as follows: a diameter greater than 10mm on axial images or central necrosis within the nodal substance. Of the 42 patients, 6 (14.3%) had pathologically positive RP nodes and of those 6 patients, 5 were able to be diagnosed preoperatively by either CT scan or MRI. Results of radiographic diagnosis (MRI or CT) were as follows: by CT scan the sensitivity, specificity and accuracy were all 100% and by MRI the sensitivity, specificity and accuracy were 83.3%, 100% and 97.0% respectively. It is our conclusion that preoperative radiographic diagnosis (MRI or CT) is very useful and effective for diagnosis of metastasis to RP nodes.