In this study, we looked for a relationship between the extent of angiogenesis and mast cell density (MCD) in human leiomyomas and endometrial carcinomas (EC), and investigated the clinicopathological relevance of mast cells (MCs) in EC. Specimens of 15 control, 20 leiomyoma, and 23 EC patients were investigated immunohistochemically using anti-CD31 and anti-tryptase antibodies. In EC, both stromal and myometrial expressions of CD31 were significantly higher than in the controls (p < 0.01 and p = 0.013; respectively). Stromal tryptase expression was not significantly lower than that of leiomyoma. In addition, in the leiomyoma group, CD31 and tryptase expressions were not much different compared to the controls. Moreover, a correlation was detected between cancer histological grade and both stromal and myometrial expressions of CD31 (p = 0.017 and p = 0.005; respectively). The findings show that high grade EC has a higher degree of vascularization than EC of lower grade, but MCD does not increase in parallel with the histological grade. This study has demonstrated that MCD does not correlate with angiogenesis and progression of grade in EC. Moreover, MCD in EC was found to be lower than in benign lesions of the uterus. In conclusion, MCs may not account for the angiogenic process which facilitates tumor growth. (C) 2011 Elsevier GmbH. All rights reserved.