Severe alterations of red blood cells from the vessels of colorectal tumors.

The RBCs from vessels supplying the tumors of 14 patients with colorectal carcinoma were examined with the scanning electron microscope. In all of them a great variety of alterations in the shape and the cell membrane were found. Erythrocytes from the vessels of healthy colonic tissue of the patients were found to have a normal appearance. Since fibrin thrombi were present in a few vessels of only six patients, the possibility that the alterations were due to mechanical trauma was not likely. This observation may serve as an additional explanation for the anemia observed in patients with colorectal carcinoma.