['Major pathology textbooks suggest that the shape of the vessel and the presence or absence of an internal elastic lamina are the best means to distinguish an artery from a vein. Because the shape of the vessel is highly dependent upon the plane of section, the internal elastic lamina is often cited as a more reliable criterion. After evaluating a patient with superficial thrombophlebitis, in whom these conventional criteria had led to a misdiagnosis of polyarteritis nodosa, we sought to determine whether the pattern of smooth muscle in the media is a more sensitive discriminator between an artery and a vein.', "Anatomically identified arteries and veins were harvested from extremity amputation specimens and stored autopsy organ specimens and reviewed by two dermatopathologists who were blinded to the gross pathologist's impression. The biopsies were assessed for the smooth muscle pattern and the presence or absence of an internal elastic lamina.", "Forty-seven of the 50 cases (94%) were concordant with the pathologist's gross impression using only the smooth muscle pattern to differentiate an artery from a vein. On the basis of the presence or absence of an internal elastic lamina, 41 of 50 cases (82%) were concordant with the prosector's designation of the vessel."] Is smooth muscle pattern more reliable than the presence or absence of an internal elastic lamina in distinguishing an artery from a vein?