MATERIALS/METHODS
A 61-year-old woman was referred to the general Otolaryngology clinic with the incidental finding of a left neck mass identified on CT scan. Contrast-enhanced CT revealed a 3cm low attenuating lesion with a punctate calcification, displacing the internal and external carotid arteries anteromedially and internal jugular vein posterolaterally(Figure 1A). The differential diagnosis included metastatic lymphadenopathy or neurogenic tumor. Given these findings, the patient was referred to interventional radiology for an image guided biopsy. However, upon review, the interventional radiology team deferred transcutaneous FNA given proximity of the mass to the great vessels. The patient was then referred to the head and neck surgical oncology clinic of the senior author for management. MRI with and without contrast demonstrated a rim-enhancing, predominantly non-enhancing lesion with a nodular enhancement at its medial portion, and foci of susceptibility effect, suggestive of microhemorrhage(Figures 1B, C). Although, schwannoma was high on the differential diagnosis, calcifications were felt to be an unusual finding. The differential diagnosis included metastatic lesions, particularly from the thyroid, and neurogenic tumor. In office US confirmed that transcutaneous biopsy was not possible due to the location of the internal and external carotid arteries in the line of transcutaneous US-guided FNA. Open biopsy was felt to be a poor choice due to potential for nerve injury in the case of a neurogenic tumor, in addition to standard reasons to avoid open surgical biopsies in cases of suspected neoplasm (scar, risk of seeding tumor, cranial nerve injury). Options of observation and EPhUS were offered and after informed consent, EPhUS was selected.
The patient was given general anesthesia and intubated orally. A tonsil gag was placed to expose the pharynx. An Olympus BF-UC180F Endoscopic Ultrasonography Bronchoscope (Tokyo, Japan) was placed transorally into the pharynx(Figure 1D). The endoscope is equipped with a 7.5 MHz convex ultrasound probe(Figure 1E). The angle of view is 90 degrees and the direction of view is 35 degrees forward and oblique. The tip of this scope contains a balloon, which assists with acoustic coupling of the ultrasound, however this is of little utility in the pharynx. A working channel allows passage of a needle for FNA. The endoscope, processing tower and monitor system allow duel display of both the ultrasound and endoscopic images, including Doppler. Both transnasal and transoral EPhUS are possible. In our experience both require two people: an endoscopist and an assistant to hold the endoscope in contact with the pharyngeal wall. The endoscope is passed into the pharynx and then brought into contact with the pharyngeal mucosa. Real time ultrasonographic imaging is then performed. In this case example, the lesion in question, with the internal and external carotid arteries on the lateral surface, are clearly identifiable (Figure 1F). After confirmation of the lesion, FNA can be performed (Figure 1G).
This needle used here is a retractable, 22g-g beveled, needle with a stylet, which allows clearance of plugs. The external surface of the needle is grooved, rendering it more hyperechoic, improving US visualization. Once the target mass is identified, the needle is advanced through the channel of the bronchoscope. Although the needle can be extended to a length of 40mm, intrinsic safety mechanisms of the device prevent excessive needle protrusion. Suction can be applied with a 20-ml VacLoc syringe as needed. When an adequate biopsy is obtained, the entire needle system is then withdrawn and the aspirated specimen is removed by pushing preservative through the lumen. Both on-site and final pathology confirmed the diagnosis of nerve sheath tumor. There was minimal blood loss. The patient was observed in the post-anesthesia unit and discharged in stable condition after examination confirmed no voice changes, dysphagia or shortness of breath. When seen in follow up, she was asymptomatic.