An Immunohistochemical Study of Angiogenesis in Tumor Emboli

ABSTRACT

BACKGROUND: Angiogenesis, which is essential for tumor growth, is known to occur in the extravascular stroma. However, vascular structures were noted in intravascular tumor emboli in surgical specimens. This prompted our investigation of the frequency and morphology of angiogenesis in tumor emboli. METHODS: Hematoxylin-eosin stained specimens were reviewed for tumor emboli, in 21 cases of stomach adenocarcinoma and 22 cases of colon adenocarcinoma. The cases were examined with immunohistochemistry using antibodies against epithelial antigen (cytokeratin), endothelial antigens (CD31, CD34), lymphatic endothelial antigen (D2-40), and proliferation-associated antigen (MIB1). RESULTS: Endothelial cells were observed in 16 tumor emboli among four (19.1%) of the 21 cases of stomach adenocarcinoma and in 32 tumor emboli among four (18.2%) of the 22 cases of colon adenocarcinoma. The endothelial cells in the tumor emboli showed papillary ingrowth from the vessel wall, formation of vascular lumens, scattered distribution, or surface coating of the emboli. Some of the endothelial cells in the tumor emboli were D2-40-positive, and some were MIB1- positive. CONCLUSIONS: These findings demonstrated that angiogenesis occurs in intravascular tumor emboli as well as in the extravascular stroma. Angiogenesis in the tumor emboli may reflect an active process and may facilitate tumor growth.