Regional differences in the intranodal distribution of tumor cells. The intranodal distribution of tumor cells was examined in 103 mesenteric and 135 axillary nodes to determine the frequency of a circumferential type of distribution and its relationship, if any, to central necrosis. Eighteen percent of the mesenteric nodes removed at surgery from patients with colon cancer contained a circumferential rim of viable tumor cells in an area corresponding wholly or in part to the normal location of the marginal sinus. In each case this rim of tumor cells surrounded a large central area of necrosis. In contrast, only one of the 135 axillary nodes removed from patients with breast cancer demonstrated this pattern. These findings suggest that by interrupting blood and lymph vessels, the circumferential spread of tumor cells underlies development of central necrosis. Previously described structural dissimilarities between mesenteric and axillary nodes may explain the striking difference in incidence of this pattern in these nodes. 