Lymphoscintigraphy accurately maps lymphatic drainage from sites of cutaneous melanoma to the draining sentinel lymph nodes. The Sydney Melanoma Unit has accumulated lymphoscintigraphy data from over 5000 patients with cutaneous melanoma over more than 15 years, collectively revealing patterns of skin lymphatic drainage. We aimed to map these data onto a three-dimensional computer model to provide improved visualisation and analysis of lymphatic drainage from sites of cutaneous melanoma.

Lymphoscintigraphy data from 5239 patients with cutaneous melanoma were collected between July 27, 1987 and Dec 16, 2005. 4302 of these patients had primary melanoma sites below the neck, and were included in this analysis. From these patients, two-dimensional lymphoscintigraphy data were mapped onto an anatomically based three-dimensional computer model of the skin and lymph nodes. Spatial analysis was done to visualise the relation between primary melanoma sites and the locations of sentinel lymph nodes.

We created three-dimensional, colour-coded heat maps that showed the drainage patterns from melanoma sites below the neck to individual lymph-node fields and to many lymph-node fields. These maps highlight the inter-patient variability in skin lymphatic drainage, and show the skin regions in which highly variable drainage can occur. To enable interactive and dynamic analysis of these data, we also developed software to predict lymphatic drainage patterns from melanoma skin sites to sentinel lymph-node fields.

The heat maps confirmed that the commonly used Sappey’s lines are not effective in predicting lymphatic drainage. The heat maps and the interactive software could be a new resource for clinicians to use in preoperative discussions with patients with melanoma and other skin cancers that can metastasise to the lymph nodes, and could be used in the identification of sentinel lymph-node fields during follow-up of such patients.