Lymphatic Drainage and Nodal Metastases
Lymph node drainage for sinonasal neoplasms is dependent on the origin of the neoplasm, the stage of the neoplasm, and the histology. Although the primary nodal drainage site for the paranasal sinuses is to the lateral retropharyngeal nodes, these lymphatics may be inconstant. Therefore, the upper internal jugular and submandibular nodes are common sites for nodal metastases. Regional lymph node metastases from sinonasal malignancies are relatively uncommon, but when present are a poor prognostic sign and usually indicative of tumor extension outside of the sinonasal cavity.143 Cervical nodal metastases are most common with tumors originating from the maxillary antrum, seen at presentation in up to 15% of cases. Nodal metastases are uncommon with ethmoid cancers, and rare with sphenoid and frontal sinus neoplasms. Up to 40% of patients with a sinonasal melanoma have cervical nodal metastases at presentation.
Less than 10% of all sinonasal carcinomas have systemic metastases. Hematogenous spread to the lungs is most common, with occasional bone metastases. The presence of cervical nodal disease places the patient at increased risk for distant metastases.143 Approximately one-half of patients with adenoid cystic carcinomas have distant metastases, most commonly to the lungs, brain, and bone.83 Hematogenous metastases are not uncommon with melanoma and affect the brain, liver, and skin. Therefore, CT imaging of the chest, abdomen, and pelvis should be included in the routine evaluation of these patients.
Imaging Following Treatment
The follow-up of patients is focused on the early detection of residual and recurrent tumors. Clinical assessment and cross-sectional imaging play complementary roles. Issues include distinguishing treatment changes from a tumor, as well as managing treatment-related complications such as cerebral radiation necrosis,144–149 carotid artery stenosis,149 xerostomia related to changes in the salivary glands included in the radiation field (associated with prominent enhancement followed by atrophy), and cranial nerve palsies.150–157