The parapharyngeal space is frequently invaded by head and neck cancer throughdirect extension, lymph node metastasis, and neural spread.
“Parapharyngeal dissection” is a method for en bloc resection of theparapharyngealspace.
To clarify the incidence, pattern, and risk factors of parapharyngeal involvement, 75 pa-tients (Stage II: 8, Stage lII: 22, Stage N: 45) who underwent parapharyngeal dissection inconjunction with ablation of the primary tumor and radical neck dissection were studiedclinicopathologically. In addition, the clinical usefulness of parapharyngeal dissection wasevaluated.
The results were as follows:
1. Tumor involvement of the parapharyngeal space was histologically confirmed in 46 pa-tients (61.3%). The primary sites of their tumors were the oral cavity in 27 patients (61.3%), the oropharynx in 9 (60.0%), the major salivary glands in 7 (50.0%), and othersites in 3 (100%).
2. The histologic patterns of the parapharyngeal involvement were direct extension of theprimary tumor in 24 patients, nodal involvement in 8, neural spread in 3, direct exten-sion combined with nodal metastasis in 10, and nodal involvement combined with neural spread in 1.
3. The risk of direct extension was significantly related to the T category, clinical stage, growth pattern, depth of invasion, and lymphatic invasion of the primary tumor.
4. There were six routes of direct extension of the tumor into the parapharyngeal space: anteromedial inferior, anteromedial superior, medial central, anterolateral, postero-lateral, and inferior.
5. Nodal spread was histologically observed in the parapharyngeal nodes, retropharyngeal nodes, and the extended nodes of Kiittner.
6. The risk of nodal involvement was significantly related to the clinical stage of the tumor.
7. Neural spread occurred via the lingual and hypoglossal nerves, and the risk of spread wasrelated to perineural invasion by the primary tumor.
8. Based on X-ray CT scans perfomed preoperatively in 69 patients, direct extension was cor-rectl ydiagnosd in 73.9%, nodal involvement in 98.6%, and neural spread in 0 %.
9. The 5-year locoregional control rate was 82.0% in this series, and 77.4% in patients withhistogically positive parapharyngeal involvement. The cause-specific 5-year survivalrate was 66.1% in this series, and 56.9% in patients with histologically provenparapharyngeal involvement. These results suggested that parapharyngeal dissection wasery useful in the management of patients with parapharyngeal involvement.