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 ( = 94) with melanoma patients without recurrence of disease ( = 288). In addition, based on conventional ( = 24) and three-dimensional photography ( = 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 ( = 94). In patients with melanoma on the lower leg ( = 31), in-transit metastases preferentially developed along anatomically predefined lymphatic pathways. In contrast when analyzing in-transit metastases of melanoma on the foot ( = 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 ( = 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.