• It is postulated that all malignant tumors spread in the same way. They invade through the basement membrane, spread through the interstitial compartment for variable distances, enter a lymphatic vessel through natural clefts, and reach the vascular compartment through lymphatic venous anastomoses or terminal lymphatics. The brain would seem to be an ideal site to test these ideas since it contains no lymphatic vessels. Injections of a well-characterized murine mammary tumor into the brains of 123 mice resulted in growth of the tumor in 82 mice (67%). Autopsy revealed only five cases in which there was distant tumor that had invaded beyond the brain.
(Arch Surg. 1992;127:389-391)