We investigated whether great tumour burden in the primary draining lymph node would lead to obstructed lymphatic flow in breast cancer patients. Breast cancer patients with false-negative sentinel lymph nodes (SLNs) were enrolled from January 2001 to March 2011, retrospectively. A further 45 breast cancer patients were recruited prospectively from December 2013 to November 2014. Carbon nanoparticles, a lymphatic tracer, were injected into the subareolar area 24 h before surgery, followed by axillary lymph node dissection. In the SLN cohort, among the 28 false-negative cases, >50 % showed great tumour burden in the axilla. In the carbon nanoparticles cohort, we found that cases with <3 nodes involved in the pathology had more lymph nodes stained by carbon nanoparticles than the subgroup with ≥3 involved nodes (P = 0.003). Nodes stained with carbon nanoparticles showed smaller tumour burdens compared with unstained nodes (P < 0.05). Furthermore, five cases showed metastatic nodes that were not stained with carbon nanoparticles, and all the lymph nodes that were free of metastasis were stained with carbon nanoparticles. Great tumour burden in the axilla might lead to lymphatic flow obstructions in clinical practice. Nevertheless, clinical trials are still needed to validate our findings.