TNM Staging Guide 5th Edition eBook

UNKNOWN PRIMARY CANCER OF THE HEAD AND NECK Unknown primary cancer of the head and neck is defined as a cancer found in a cervical lymph node without any identifiable primary lesion in the head and neck and nothing to suggest that this is a distant metastasis from another body site. The majority of these lesions present as a lateral neck mass, representing regional spread to a level II or III lymph node. Potential primary sites can be within any of the head and neck subsites, but the most common sources are the nasopharynx, oropharynx, and thyroid. The latter two sites often can produce cystic lesions that may mimic branchial cleft anomalies. As a result, it is critical for there to be an appropriate level of suspicion for malignancy for any adult patient with a cystic neck mass. Evaluation of these lesions includes a detailed head and neck history and physical exam, including thorough inspection and palpation of the oropharynx as well as a fiberoptic nasopharyngolaryngoscopy. Additional imaging should also be obtained of the neck mass, typically with a contrasted neck CT scan or PET/CT and the neck mass should be biopsied with a fine needle aspiration. Such aspirations should be done with ultrasound guidance to ensure a high quality specimen is obtained from the solid portion of the mass, and all tissue should be evaluated for p16 staining as well as EBV. Following this initial outpatient work-up, the next step should include and exam under anesthesia and panendoscopy to look for a potential primary lesions. If none are found, a palatine and lingual tonsillectomy should be considered [for p16+ neck nodes] along with directed biopsies of the nasopharynx [especially for EBV(+) neck nodes]. If the primary lesion is still not identified through this work-up, the patient should be managed as an unknown primary head and neck cancer. Of note, for neck nodes that are p16+ or EBV (+) with no identifiable primary site, they should be treated as T0 tumors of the oropharynx or nasopharynx, respectively, rather than as unknown primary cancers. Treatment of unknown primary head and neck cancer can be done using a surgical or non-surgical approach. For surgical patients, an upfront neck dissection can be performed, using radiation or chemoradiation therapy adjuvantly, as indicated based on the pathology. For p16+ disease, radiation fields typically are expanded to cover the oropharynx for potential subclinical lesions, with analogous coverage of the nasopharynx for EBV(+) disease. For non-surgical regimens, chemoradiation therapy is typically employed, with surgery only being used for residual disease after treatment.

8 TNM Staging of Head and Neck Cancer and Neck Dissection Classification