Transoral Endoscopic Ultrasound-Guided Fine-Needle Biopsy of Parapharyngeal Space Tumors: Evaluation of Feasibility, Diagnostic Yield, and Safety (With Video).

Tumors of the parapharyngeal space (PPS) are difficult to biopsy because of their deep location and proximity to major neurovascular structures. Existing percutaneous, transoral, and transnasal approaches have limitations and variable success. This study evaluated a novel transoral biopsy technique for PPS tumors using a flexible echoendoscope for endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB). We retrospectively reviewed adults with PPS tumors who underwent transoral EUS-FNB at a tertiary cancer hospital from January 2020 to April 2025. Under deep intravenous sedation, the echoendoscope was advanced transorally into the oropharynx and torqued toward the tumor side. The EUS transducer was positioned against the lateral pharyngeal wall to visualize the lesion. EUS-FNB was performed using end-cutting needles, suction, and fanning or torquing technique. Samples were assessed macroscopically for tissue cores and processed for histopathology. Data on tumor characteristics, technical success, diagnostic yield, and adverse events were collected. Twenty-one patients were included (median tumor diameter 30 mm; interquartile range, 18-37). Tumors were successfully visualized and biopsied in 18 of 21 patients, and all samples were diagnostic. Visualization failed in three patients; the technical success and diagnostic yield were both 86% (95% CI, 65-96). Adverse events occurred in 6 of 18 patients (33%; 95% CI, 16-56) and were mostly mild: five AGREE grade I events (self-limiting sore throat) and one grade II event (parapharyngeal inflammation treated with antibiotics). Transoral EUS-FNB appears to be a feasible and minimally invasive technique for diagnosing PPS tumors with a high diagnostic yield and an acceptable safety profile in selected patients.