Procoagulant activity of human tumours: existence of Xa and thrombin-like activities.

We have analysed 15 infiltrating duct carcinomas of the breast, 10 gastrointestinal adenocarcinomas, one each of the thyroid and larynx, and four mesenchymal tumours for the presence and the nature of procoagulant activity (PCA). The metastatic tumours had a significantly higher PCA (P = 0.01-0.001) as compared to the non-metastatic tumours in the respective groups, and almost 20-25 times the activity as compared to normal tissue (P = 0.001). Although the majority of the tumours had FVII-dependent tissue thromboplastin-like activity, some of the tumour homogenates revealed the presence of an FVII-independent PCA. Unlike the known alternate PCA, which acts via factor X activation, this PCA was factor X independent. It caused clot formation in FX-deficient plasma (six cases) and purified fibrinogen solution (four cases), indicating the presence of a Xa-like enzyme or a thrombin-like activity respectively.