Prevalence of contralateral lymphatic drainage patterns during sentinel lymph node biopsy for truncal melanoma: A...

This study aimed to examine the prevalence, patterns, and outcomes of contralateral lymphatic drainage during sentinel lymph node biopsy (SLNB) in patients with truncal melanoma. Understanding this phenomenon is crucial for improving surveillance and management strategies for melanoma patients.

This retrospective cohort study analysed 1308 consecutive patients aged 18 years and over who underwent wide local excision (WLE) for truncal melanoma followed by SLNB at The Christie Hospital, Manchester, UK, between October 2006 and November 2024. Exclusions included non-truncal melanoma and cases without lymphoscintigraphy data. SLNB evolved from intradermal injections of blue dye to include radiolabelled Technetium-99m-nano colloid. Contralateral drainage was defined as sentinel lymph nodes draining exclusively to the opposite side of the coronal midline relative to the WLE scar. Data were correlated with imaging results and patient outcomes.

Contralateral drainage occurred in 14 patients (1.1%). This subgroup had melanoma thicknesses ranging from 0.80 to 6.40 mm and included 8 males and 6 females (ages 26-72 years). Notably, 10 cases involved posterior torso melanomas, with 6 located on the lower back. Three patients (21.4%) experienced melanoma recurrence during follow-up, all on the ipsilateral side. One patient treated in 2007 died following recurrence, while 2 patients treated in 2018 and 2021 remain alive following immunotherapy.

Contralateral sentinel lymph node drainage, though rare, highlights the need for tailored surveillance strategies for patients with truncal melanoma, particularly those with posterior torso lesions. These findings underscore the importance of incorporating this data into patient consent and individualised care plans.