Endoscopic resection for superficial pharyngeal carcinoma has been reported as a minimally invasive therapeutic option; however, the pharyngeal space is anatomically narrow, making the procedure technically challenging. We developed the underwater ESD with Water Pressure Method (WPM), which utilizes endoscopic waterjet pressure under immersion to facilitate submucosal entry, and previously reported its usefulness in pharyngeal ESD. In the narrow working space of the pharynx, a thin therapeutic endoscope may provide additional technical advantages. This study evaluated the short-term treatment outcomes of pharyngeal ESD performed using WPM with a thin therapeutic endoscope.

We retrospectively reviewed lesions treated with pharyngeal ESD using WPM and a thin therapeutic endoscope under general anesthesia with laryngeal exposure at our institution between March 2022 and May 2025. Short-term outcomes were assessed. The submucosal dissection speed was compared with that of lesions treated during the same period using a conventional-diameter therapeutic endoscope.

During the study period, 27 pharyngeal ESD procedures were performed, of which 10 patients with 11 lesions were treated using the thin therapeutic endoscope. All lesions were located in the hypopharynx: 3 in the pyriform sinus, 1 in the post-cricoid area, and 7 on the posterior wall. The median tumor diameter was 20 mm (range, 5–40 mm). Both the en bloc resection rate and procedural completion rate were 100%, and the histological R0 resection rate was 82%. The median procedure time was 14 minutes (range, 5–67 minutes). The median hospital stay was 6 days (range, 6–8 days).

During the same period, 17 patients with 20 lesions underwent ESD using a conventional-diameter therapeutic endoscope. The median dissection speed was faster with the thin therapeutic endoscope than with the conventional endoscope (22.7 vs. 15.5 mm²/min). No adverse events—including laryngeal edema, postoperative bleeding, or aspiration pneumonia—were observed.

In the anatomically narrow pharyngeal region, WPM-assisted ESD using a thin therapeutic endoscope enabled safe and efficient dissection, achieving a faster dissection speed compared with conventional-diameter endoscopes. This approach appears particularly useful for pharyngeal ESD in limited working spaces.