Introduction: Early conventional lymphoscintigrams can distinguish sentinel nodes from second-tier nodes and the new SPECT/CT technology shows their precise anatomical location. The purpose of the study was to analyze lymphatic drainage patterns to the groin using these techniques and to determine the implications for a potential groin dissection.
Methods: Fifty-five groins in 50 patients were analyzed using lymphoscintigrams and SPECT/CT. The superficial groin was divided in five Daseler-zones, and the pelvic region in three zones.
Results: A total of 106 sentinel nodes were depicted: 10% in the superior lateral, 13% superior medial, 42% inferior medial, 26% central, and 8% in the external iliac zone. The second-tier nodes were mostly visualized in the external iliac zone (54%). No drainage at all was seen to the inferior lateral zone. In lower trunk melanoma, 81% of the sentinel nodes were in the superior and central zones, and no second-tier nodes were observed in the inferior zones. Twelve sentinel nodes were involved: ten in the inferior medial and two in the central zone.
Conclusions: Most (involved) sentinel nodes were found in the inferior medial and central zones. The high frequency of pelvic second-tier nodes indicates the need for a deep completion groin dissection in the majority of patients with positive sentinel nodes. In none of the patients, lymphatic drainage was seen to the inferior lateral zone, which suggests that this area need not be included in a completion dissection. In patients with lower trunk melanoma, the inferior medial zone may not need to be removed either.