Conventional and Three-Dimensional Photography As a Tool to Map Distribution Patterns of In-Transit Melanoma Metastases on the Lower Extremity

Background In melanoma, in-transit metastases characteristically occur at the lower extremity along lymphatic vessels. Objectives The objective of this study was to evaluate conventional or three-dimensional photography as a tool to analyze in-transit metastasis pattern of melanoma of the lower extremity. In addition, we assessed risk factors for the development of in-transit metastases in cutaneous melanoma. Methods In this retrospective, monocentric study first we compared the clinical data of all evaluable patients with in-transit metastases of melanoma on the lower extremity ( n = 94) with melanoma patients without recurrence of disease ( n = 288). In addition, based on conventional ( n = 24) and three-dimensional photography ( n = 22), we defined the specific distribution patterns of the in-transit metastases on the lower extremity. Results Using a multivariate analysis we identified nodular melanoma, tumor thickness, and ulceration as independent risk factors to develop in-transit metastases ITM ( n = 94). In patients with melanoma on the lower leg ( n = 31), in-transit metastases preferentially developed along anatomically predefined lymphatic pathways. In contrast when analyzing in-transit metastases of melanoma on the foot ( n = 15) no clear pattern could be visualized. In addition, no difference in distance between in-transit metastases and primary melanoma on the foot compared to the lower leg was observed using three-dimensional photography ( n = 22). Conclusion A risk-adapted follow-up of melanoma patients to detect in-transit metastases can be applied by knowledge of the specific lymphatic drainage of the lower extremity. Our current analysis suggests a more complex lymphatic drainage of the foot.