Contralateral sentinel node drainage patterns in early lateralised oral squamous cell carcinoma – a retrospective study

Introduction Sentinel lymph node biopsy (SNB) maps tumour draining lymph nodes on an individual basis, identifying locations outside typical neck dissection levels including the contralateral neck. We report contralateral drainage and positivity rates in lateralised early oral cavity squamous cell carcinoma (OCSCC) and assess associations with tumour characteristics. Methods Single-centre retrospective study of patients with lateralised cT1-T2 OCSCC treated with wide local excision and SNB between February 2016 and January 2022. Data included tumour depth, distance to midline, lymphatic drainage, sentinel node number/location and SNB status. Variables were analysed using two-tailed Student t-tests and Fisher's exact test, with Holm-Bonferroni correction where appropriate. Results Ninety-two patients underwent SNB; sixty-four met criteria for lymphatic drainage analysis. Contralateral or bilateral drainage occurred in twenty-six (40.6%) cases. Fifty (78.1%) tumours involved the anterior 2/3 tongue, with contralateral or bilateral drainage in twenty (40.0%). Twenty-two patients (34.4%) had positive SNB, including three (4.7%) with contralateral metastases. Mean follow-up was 46.3 months. One- and three-year overall survival were 93.7% and 77.8%; disease-free survival was 91.7% and 80.0%. One patient (1.5%) had a false-negative SNB, and three (4.7%) would have been inadequately staged or treated by ipsilateral elective neck dissection. Discussion Contralateral drainage was common in lateralised early OCSCC, although contralateral positivity was uncommon. SNB may improve individualised staging by identifying clinically relevant contralateral drainage not addressed by ipsilateral elective neck dissection. Prospective multicentre studies are needed to define anatomical and tumour-related predictive factors for contralateral drainage.