Tissue factor expressed in pituitary adenoma cells contributes to the development of vascular events in pituitary adenomas.

BACKGROUND: Tissue factor (TF) was initially identified as an important factor in the initiation of coagulation. TF has recently been found to be expressed highly in certain types of malignant tumors. It has also been reported to be involved in systemic coagulopathy in cancer patients and in the proliferative and invasive activities of tumor cells. Tissue factor pathway inhibitor (TFPI) is a strong biologic inhibitor of TF. To the authors' knowledge, this is the first study of the expression of TF and TFPI in human pituitary adenoma.
METHODS: The expression of TF and TFPI were analyzed by immunohistochemical methods in human pituitary adenoma samples. To examine whether TF and TFPI expression influence the proliferative and/or invasive character of pituitary adenomas, the authors determined the MIB-1 labeling indices and invasiveness of all the pituitary adenomas they examined. Furthermore, to determine whether TF contributes to coagulation inside adenoma tissues, the incidence of cysts or hematomas in adenomas was analyzed.
RESULTS: In cells from 29 of 83 pituitary adenomas, overexpression of TF was observed. This was not the case for normal pituitary gland cells. TFPI was not expressed in either the adenomas or the normal pituitary glands from adenoma-bearing individuals. The expression of TF was significantly correlated with the formation of cysts or hematomas in pituitary adenomas. However, no such correlation with either the proliferative activity or the invasive character of the adenomas was observed.
CONCLUSIONS: Locally overexpressed TF in adenoma cells may contribute to the development of vascular events, such as infarction and/or hemorrhagic infarction, in pituitary adenomas. Copyright 1999 American Cancer Society.