Detecting atypical sentinel lymph nodes in early-stage cervical cancer using a standardized technique with a hybrid tracer

Abstract Background Since October 2018, lymph node (LN) status has become part of the International Federation of Gynaecology and Obstetrics (FIGO) staging, given that it is one of the most important prognostic factors among women with cervical cancer (CC). The aim of this study was to determine the rate of atypical lymphatic drainage in patients with clinical early-stage CC using a hybrid tracer (ICG-99mTc nanocolloid). Methodology A prospective, observational, descriptive, single-centre study conducted at Son Espases University Hospital between January 2019 and October 2023. Patients with clinical early-stage CC who underwent SLN mapping during surgical staging were included. External iliac and obturator nodes were defined as common SLN locations. Para-aortic, common iliac, presacral, internal iliac, and parametrial nodes were defined as uncommon (atypical) locations. Results Thirty-nine cases of CC were included. Overall SLN detection rate was 97.4%, with 89.5% bilaterally. Positive SLNs were found in 21.1% of patients. Atypical lymphatic drainage was present in 8 out of 38 (21.1%). Of the total SLNs (146), 10.3% corresponded to an atypical zone (the most frequent, common iliac vessels). SLNs in the atypical area had a higher proportion of metastasis than the usual area (37.5% vs. 16.7%; p=0.327). Parametrial nodes were detected in 17.9% of patients; two of these (5.2%) with the presence of metastases. In all cases where a parametrial SLN was detected, drainage was also observed to a SLN in a common location. There was no involvement of parametrial lymphatic channels or parametrial nodes in any patient (7/8, 87.5%) with metastatic pelvic SLNs. Conclusion SLN biopsy can detect unusual drainage in a significant proportion of patients with CC. SLNs in atypical locations have a higher percentage of metastatic involvement, which consequently improves staging and tailoring therapy. Our series suggests that lymphatic drainage from the cervical tumour to the pelvic nodes could be a direct route that bypasses parametrial nodes. We suggest that SLN mapping performed by a standardized surgical technique using a hybrid tracer (ICG-99mTc) could help in the identification of the "true sentinel lymph node" and ensure no empty node packet is obtained.