The adhesion of thromboplastic tumour emboli to vessel walls in vivo.

Abstract

The ultrastructure of adherent tumour emboli in vivo was examined using suspensions of a transplantable thymic lymphoma in mice and Walker 256 carcinoma in rats, injected into the inferior vena cava following mechanical damage to its wall. Two types of adherent tumour emboli were observed and these were characterized by the presence or absence of damage to the underlying vessel wall. Where the endothelium was intact the tumour cells were attached to platelets and to a relatively thin layer of fibrin or fibrin-like material which enclosed the tumour-platelet aggregate. Multivesicular membranous sacs were seen in association with the platelets in the tumour-platelet body. Where damage had resulted in exfoliation of the endothelium, fibrin formed the principal “glue” between the tumour cells and the vessel wall. The fibrin was of a type of structure usually associated with monomeric or low polymeric forms and without cross-striations. There appeared to be no hindrance to the progression of tumour cells through this fibrin, in contrast to the intima with intact endothelium. The possible correlation of these findings with Wood's cinephotomicrographic observations on rabbit V2 carcinoma emboli is discussed.