Intratumoral distribution of microspheres.

Fifteen mu carbonized microspheres injected in two transplantable rat tumors, a hepatoma transplanted to the dorsum of one hindpaw and an adenocarcinoma transplanted into the liver, were found to be unevenly distributed and often in aggregates that seemed to fill intratumoral vessels. This finding can partly explain the increased vascular resistance in tumors after microsphere injection and makes the technique with repeated injections of microspheres disputable.