Patterns of node mapping differ for axial and extremity primary cutaneous melanoma: A case for a more selective use of pre-operative imaging.

Purpose: Preoperative lymphoscintigraphy for sentinel lymph node mapping in melanoma improves the ability to locate nodes. However, it still remains unclear whether this step is required for all patients.

Methods: Patients diagnosed with cutaneous melanoma from 1996 to 2012 were identified. Exclusion criteria were in situ disease, metastatic disease, or no SLN biopsy.

Results: 214 patients were evaluated. Median age was 57 years, the majority were male (59.8%), white (97.2%), and stage I (60.7%). SLN revealed metastatic disease in 14.5% of patients. The most common primary site was the trunk (43.4%) followed by head and neck (21%), upper extremity (19.2%), and lower extremity (16.4%). Multiple lymphatic basins were most common for head and neck lesions (66.7%) followed by those on the trunk (28.8%), with fewer identified when lower (11.4%), and upper extremities were involved (4.2%). When comparison was restricted to extremity vs. axial, a single basin was noted in 94.5% vs. 59.9% of patients, p < 0.0001. For all extremity lesions the SLN was located in the primary basin. Additional sites included in-transit (popliteal) and second tier basins. The only melanomas with bilateral or contralateral SLN were axial melanomas.

Conclusions: Patients with axial melanomas benefit most from lymphoscintigraphy. This step may not be required for extremity melanoma.