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Previous studies have shown that independent of tumor size, palpable breast tumors have a higher incidence of lymph node metastasis compared with nonpalpable tumors. This study further examines this phenomenon using a large sentinel lymph node (SLN) database. Data from a prospective, institutional review board (IRB)-approved, multi-institutional study from the University of Louisville Breast Cancer Sentinel Lymph Node Study Group was used. From August 1997 through December 2001, 3192 patients with clinical T1 and T2 N0 breast cancer underwent SLN biopsy, most with a combined technique of radioactive colloid and blue dye, followed by level I/II axillary dissection. Patients with palpable tumors tended to be younger (mean age 58 years) compared with nonpalpable tumors (mean age 61 years). The incidence of positive axillary metastasis was significant between palpable and nonpalpable tumors (43% and 23%, respectively), independent of tumor size by logistic regression (p = 0.0001). The SLN identification rate was significantly different between palpable and nonpalpable tumors (95% versus 91%, respectively; p < 0.0001). A unifying theory to explain the phenomenon that palpable tumors, stage for stage, are associated with a higher rate of nodal metastasis is that palpable tumors are, on average, closer to the skin and the rich network of dermal lymphatics. We believe that the dermal lymphatics of the breast represent a clinically relevant metastatic pathway to the axilla. [ABSTRACT FROM AUTHOR]

Increasing tumor burden in the axilla, as determined by the number of positive lymph nodes, adversely affects sentinel lymph node (SLN) identification and false-negative rates. The University of Louisville Breast Cancer Sentinel Lymph Node Study is a prospective, multi-institutional study. All enrolled patients underwent SLN biopsy, followed by complete level I/II axillary dissection. Participating surgeons represent a variety of practice settings, mostly community-based private practice. A total of 229 surgeons enrolled 2206 patients between August 1997 and November 2000. SLN biopsy was performed using blue dye injection alone, radioactive colloid alone, or a combination of the two agents. Two key parameters used to measure SLN biopsy success are the SLN identification rate and SLN false-negative rate. The overall SLN identification and false-negative rates were 92.5% and 8.0%, respectively. With increasing numbers of positive axillary nodes, there was a decreased sentinel node identification rate. There was no difference in the false-negative rate with increasing axillary tumor burden. Increased tumor burden in the axilla (as determined by the mean number of positive nodes) is associated with failure to identify a SLN in some cases, but is not an explanation for false-negative results. Standard axillary dissection should be performed when a SLN cannot be identified. [ABSTRACT FROM AUTHOR]