Supplementary Material for: Safety of Argon Plasma Coagulation for Minute Synchronous Neoplasms Detected under General Anesthesia during Endoscopic Laryngopharyngeal Surgery: A case series

Introduction: Despite the use of narrow-band imaging, comprehensive endoscopic evaluation of the laryngopharynx in the endoscopy suite remains challenging because of its complex anatomical structure, limited working space, and reactions such as gagging and coughing. Consequently, minute synchronous neoplasms may occasionally be overlooked during the initial endoscopic assessment. We hypothesized that argon–plasma coagulation (APC) could serve as a minimally invasive treatment for minute synchronous neoplasms of the head and neck detected during endoscopic laryngopharyngeal surgery combined with endoscopic submucosal dissection (ELPS/ESD) for primary lesions. Case presentation: We report three cases of pharyngeal cancer treated with ELPS/ESD under general anesthesia: an 82-year-old man, a 73-year-old man, and a 40-year-old woman. During intraoperative endoscopic observation, nine minute lesions measuring 3–7 mm that had not been detected in the endoscopy suite were identified in three patients. These lesions were immediately treated with APC, a non-contact technique that uses ionized argon gas to coagulate abnormal tissue. In Cases 1, 2, and 3, the lengths of hospital stay were 10, 11, and 6 days, respectively, and the follow-up periods were 9 months, 6 months, and 6 months, respectively. Within this limited follow-up period, no post-procedural bleeding, post-procedural hoarseness, or post-procedural swallowing dysfunction was observed. Conclusions: Based on this small case series with limited follow-up, intraoperative APC may be a feasible adjunctive approach for the ablation of minute synchronous lesions detected during ELPS/ESD for pharyngeal cancer.