Lymphatic vessel density in primary melanomas predicts sentinel lymph node status and risk of metastasis

Aims: Important prognostic factors in patients with cutaneous melanoma include primary tumour thickness/depth of invasion, ulceration and mitotic rate, and the presence of tumour cells in regional lymph nodes. More recently, features of stromal components, such as blood and lymphatic vessel density, have been suggested as additional indicators of metastatic potential. Our aim was to investigate the relationship between tumour lymphatic vessels and lymph node metastasis. Methods and results: Metastasizing (n = 11) and non-metastasizing (n = 11) primary melanoma samples matched for depth/thickness, mitotic rate and ulceration were examined for lymphatic vessel density (LVD) in the primary tumour, using an antibody to podoplanin. Significant differences were found between LVD (vessels/unit area) in the peripheral (5.73 +/- 0.67) versus central (1.72 +/- 0.42) regions of the metastasizing tumour group (P < 0.001), and between LVD in the peripheral areas of metastasizing (5.73 +/- 0.67) versus non-metastasizing (4.21 +/- 0.37) tumours (P < 0.01). No overall difference was found between total average LVD in the two tumour groups or between their vessel morphology. Conclusions: Our results show that LVD is associated with risk of lymph node metastasis. Furthermore, the ratio of peripheral LVD: central LVD is a useful marker of primary melanomas that are likely to metastasize to lymph nodes.