Background：CD34 is a kind of single strand transmembrane protein with a molecular weight of 110 kDa, which is the main marker of hematopoietic stem cell myeloid cells and vascular endothelial cells. CD34 can identify the differentiation of endothelial cells, but the identifying sensitivity has no relation with the grading of tumor. CD34 is expressed positive in more than 85％ of angiosarcoma and Kapois' s sarcoma expressed. It can be applied in combination with CD117 for differential diagnosis of gastric stromal tumors. In general, CD34+ can be identified with CD34- in solitary fibrous tumors, and the identification between CD34+ of dermatofibrosarcoma protuberans and CD34- of benign fibrous histiocytoma, CD34- of spindle cell carcinoma in breast and CD34+ if malignant phyllodes tumor. And it can also be used to research the angiogenesis during a variety of tumor interstitial.
