TLR4 and neoplasm: HMGB1 secreted by keratinocytes in response to UV induces the activation of TLR4 signaling which enhances the migration of melanoma cells, furthering the hypothesis that TLR4 plays a pivotal role in UV-driven progression and metastasis of this tumor, thus explaining one of the main features of melanoma, which is linfovascular metastatization [30].