Background: Clinicians often rely on primary tumor characteristics to decide on adjuvant treatment for patients with breast cancer with isolated tumor cells (ITC) in the sentinel lymph node. The purpose of this study was to determine if there is a significant difference in primary tumor characteristics between ITC and other nodal groups. Methods: Patients undergoing sentinel lymphadenectomy were divided into 3 groups: N0, no metastases; ITC, metastasis less than 0.2 mm; and micro- or macrometastases (MM), metastasis greater than 0.2 mm. The chi-square test and analysis of variance were used. Results: A total of 552 patients underwent sentinel lymphadenectomy; 197 (36%) had tumor-positive sentinel lymph nodes. Of these, 35 (18%) were classified as ITC and 162 (82%) as MM. When primary tumor characteristics were compared, the ITC group had significantly more lymphovascular invasion and higher proliferative rate than the N0 group (P < .05) and significantly less lymphovascular invasion, lower proliferative rate, and smaller tumor size (P < .05) than the MM group. There were no significant differences in the age, hormone receptor status, histologic type, or tumor grade among the patient groups. Conclusions: Proliferation and lymphovascular invasion of the primary tumor are significantly different between the ITC, N0, and MM groups suggesting that ITC tumors may have different biology than the N0 or MM tumors.
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