50 patients with suspected or confirmed OPC will undergo a transcervical ultrasound during their first visit at the Vanderbilt Head and Neck Clinic in addition to other imaging modalities (CT, MRI and/or PET) as indicated as part of routine clinical care; patients will also be asked to provide a blood specimen. Ultrasound exams will be performed by a clinician blinded to details of the case. All patients will have a CT as part of their diagnostic work-up. Sensitivity of ultrasound to detect tumors identified by CT will be determined. Approximately 40% of patients are expected to test negative on CT requiring MRI and/or PET imaging. Among this subset, the sensitivity of ultrasound to detect tumors identified by either PET and/or MRI will be determined. Tumor size will be determined by 3 ultrasound measurements along the largest diameter of the tumor; agreement between ultrasound and the clinical imaging modalities will be calculated. The investigators will recruit an additional 78 OPC patients with pre-treatment serum banked within the Vanderbilt Head and Neck Cancer Biorepository (18 HPV-negative, 60 HPV-OPC) for HPV serologic analyses; total: 128 samples. Sensitivity and specificity of HPV16 E6 antibodies for detecting HPV-OPC will be calculated. As an exploratory aim, the proportion of tumors undetectable by CT, PET, and MRI, but detected by ultrasound will be determined.