Vimentin expression appears to be associated with poor prognosis in node-negative ductal NOS breast carcinomas. Vimentin expression in tumors from 83 node-negative and 112 node-positive patients with infiltrative ductal not otherwise specified (NOS) breast carcinomas has been compared with 5-year survival. For node-negative, but not for node-positive patients, there was a significant inverse relation between vimentin expression and survival. Five-year survival of node-negative patients with vimentin-positive tumors was significantly worse compared with vimentin-negative tumors (P less than 0.0001). In the node-negative group, only 36% of patients with vimentin-positive tumors but 82% of patients with vimentin-negative tumors survived 5 years. Tumors of all eight node-negative patients with ductal NOS cancer who died in the first 27 months expressed vimentin. Multivariate analysis of the node-negative group showed a strong correlation of vimentin expression and overall survival, but weak and not significant correlation between histologic grade or size and overall survival at 5 years. Thus vimentin expression seems to be a strong indicator of poor prognosis in node-negative ductal NOS breast carcinomas. 