Cutaneous malignant melanoma: correlation between neovascularization and peritumor accumulation of mast cells overexpressing vascular endothelial growth factor

To investigate the possible role of mast cells (MC) in the angiogenic process in cutaneous melanoma, we examined tissue samples from 35 adult patients with primary malignant melanoma and compared with 20 intradermal benign nevi. MC were identified by anti-tryptase, microvessels by anti-CD34, and vascular endothelial growth factor (VEGF) expression by standard immunohistochemical methods. Tryptase-positive MC expressing VEGF were identified by double immunostaining. The numbers of MC and microvessels around the tumor were determined by the point counting method. MC density was significantly greater in melanoma compared with benign nevi (197.6 +/- 19.4 v 95.7 +/- 5.0/mm2, P < .001). Vascular density was also significantly higher in melanoma than in benign lesions (3.6-fold, P < .001). Double immunostaining showed the presence of VEGF in the cytoplasm of tryptase-positive peritumoral MC. The percentage of this MC-subtype was significantly higher in melanoma than in nevus tissues (71.9 +/- 2.4% v 30.6 +/- 2.5%, P < .001). A strong significant correlation was shown between the number of VEGF+ MC and microvessel density (r = .811, P < .001). MC count and VEGF+ MC count, as well as microvessel density were significantly higher in aggressive (metastasizing) melanomas (P < .001). Our results suggest that peritumoral accumulation of MC and the subsequent release of potent angiogenic factor such as VEGF may thus represent a tumor-host interaction that may favor progression of this tumor.