S. Noorbakhsh1, K. Olino2, S. Weiss2, D. Pucar2, S. Ariyan2, J. Clune2 1West Virginia School of Medicine,Morgantown, WV, USA 2Yale University School Of Medicine,New Haven, CT, USA
Introduction:
Sentinel lymph node biopsy (SLNB) for invasive auricular melanoma is standard of care. However, lymphatic drainage from the ear is incompletely understood. The goals of this study are to: 1) assess lymphatic draining patterns in auricular melanoma and 2) to prospectively compare pre-operative lymphoscintigraphy and intra-operative radioisotope sentinel node identification to determine if the methods are equally effective.
Methods:
From 1997-2018, patients with melanoma of the ear requiring SLNB were prospectively evaluated with pre-operative lymphoscintigraphy followed by intraoperative radioisotope identification. To identify this cohort of patients, 122 consecutive cases of invasive auricular melanoma were reviewed. Lesion site, pathology, demographic information, and outcomes data were recorded for each patient. Both pre-operative lymphoscintigram and SLNB were performed in 64 patients. Site of pre-operative mapping and site of sentinel node biopsy were recorded as parotid, mastoid, and/or cervical (I-V) for each patient. Comparisons between preoperative lymphoscintigraphy and intraoperative radioisotope identification were made at both the individual level and in aggregate.
Results:
Sixty-four patients underwent both pre-operative lymphoscintigram and intra-operative injection of radiotracer with SLNB in this study. On pre-operative lymphoscintigram, 89.1% showed pre-operative drainage to cervical levels I-V, 21.9% showed drainage to the parotid region, and 4.7% showed drainage to the mastoid region. In contrast, intra-operative biopsy was taken from the cervical region in 95.3% of cases, the parotid region in 43.8% of cases, and the mastoid region in 17.2% of cases. Significantly more parotid nodes (p=0.01) and mastoid nodes (p=0.03) were biopsied intra-operatively than were mapped pre-operatively. In total, 33 nodes were biopsied intra-operatively that were not mapped pre-operatively, the majority in the parotid and mastoid regions. Additionally, there were no cases of pre-operative lymphoscintigraphic mapping or intra-operative SLNB outside of the head and neck.
Conclusion:
In this study, higher rates of intra-operative sentinel lymph node identification relative to pre-operative mapping indicate that sole reliance on pre-operative lymphoscintigraphy may be insufficient in the operative planning and treatment of auricular melanoma. Our data indicate that the surgeon should diligently survey the head and neck intra-operatively with radioisotope injection and gamma probe to uncover sentinel nodes not visualized pre-operatively. Furthermore, the ipsilateral parotid and mastoid regions require particular attention during intra-operative sentinel node identification. Lymphatic drainage from the ear occurs reliably to the ipsilateral head and neck, and the parotid and mastoid regions were sites of frequent biopsy in our study without corresponding pre-operative mapping.