Limiting Vascular Diameters in Various Organs

THE appearance of tumor cells in peripheral blood drawn from the antecubital vein in patients with various visceral cancers has been frequently reported.1-3Depending upon the location of the primary tumor or its known secondaries, these cells would have traversed one or more organ vascular beds. Tumor cells are generally larger than the normal formed elements of the blood, a factor of possible importance in their arrest and subsequent development into metastases. Certain tissues and organs, including those of the distribution drained by the antecubital veins, are rarely the site of metastatic implant. It could be inferred from the clinical studies on antecubital vein blood that such tumor cells had either passed through or around the capillary beds of hand and forearm unimpeded and, hence, produced no metastases. There is no evidence, however, that other tumor cells had not entered these capillary beds, lodged, and become nonviable. Three possibilities