Immunohistological distribution of stem cell factor and kit receptor in angiosarcoma

Angiosarcoma is a rare neoplasm, originating in the endothelium, which has a poor prognosis because of a high potential for metastasis. Although little is known about the pathogenesis of angiosarcoma, angiogenic cytokines are suggested to play an important role in tumor progression in a paracrine/autocrine fashion. Mast cells contain several mediators or cytokines influencing vascularization. To clarify the role of mast cells in angiosarcoma, mast cells were counted in primary lesions of angiosarcoma (n=7). The results showed that the number of mast cells in the lesional skin of angiosarcoma (91.2+/-14.6/mm2) was significantly increased compared to that in normal skin (30.1+/-4.6/mm2) (p < 0.001). Immunohistological localization of stem cell factor, a mast cell growth factor, demonstrated that stem cell factor-positive cells occurred in the tumors forming the vascular lumen in nodular-type angiosarcoma. In macular angiosarcoma, stem cell factor was also detected in the tumor vascular endothelial cells. Infiltrating mast cells were positive for the kit receptor in both types of angiosarcoma. These results suggest that tumor cell-derived stem cell factor may play a role in the increased number of mast cells, via the kit receptor, which may contribute to the proliferation of tumor cells, leading to the progression of angiosarcoma.