Ultrasound Guided Methylene Blue Injection for Deep Margin Localization of Early-Stage Oral Tongue Carcinoma

Introduction: Margin status of oral tongue squamous cell carcinoma (OTSCC) is a significant postoperative prognosticator. Presence of microscopically positive disease or close margin portends poor locoregional (LR) control and decreases survival. Resection techniques vary and the deep margin is the most commonly implicated positive margin. We propose a real-time intraoperative technique that uses ultrasound (US) guidance to mark anticipated deep margin which will then provide visual cue during resection that appropriate depth has been maintained.

Methods: Patients with cT1-2 OTSCC were reviewed. Required equipment includes: US with a high-resolution linear-array transducer (8–15 MHz) and 50 mg/10 mL methylene blue (MB). 0.5mL MB is placed in a 3 mL syringe.

Prior to incision, US is used to localize the deepest aspect of the tumor. A 25-gauge needle is passed under US guidance using in-plane technique to the region of desired resection, typically located 1 cm deep to the tumor, and 0.5 mL of MB is injected. Dissection proceeds circumferentially and deeper until MB is visualized. This visual cue provides confirmation that the preoperative anticipated deep margin has been maintained during the course of dissection. Intraoperative frozen section analysis of both peripheral and deep margins is then performed on the specimen.

Results: LR recurrence is 6 times higher with positive margins versus negative margins greater than 2.2 mm. Additionally, re-resection of a positive margin, even if negative margin is achieved, negatively impacts overall and LR free survival. US guided OTSCC resection significantly improves negative margins versus conventional technique.

Guided MB margin localization is a fixed visual cue of the deep margin prior to manipulation of the tissues, in addition, intraoperative use of US during course of resection is limited by the presence of air gap between the tumor and operative bed during retraction which will adversely impact transducer image.

Conclusions: We present a dynamic and novel technique which allows for accurate US-guided marking of intended deep margin for early stage OTSCC malignancies.