Epitrochlear and Humeral Lymph Nodes: A Biomarker for Deep Lymphatic Function and Implications for Breast Cancer-Related Lymphedema Risk.

Background: Superficial to deep system rerouting of lymph protects against breast cancer-related lymphedema (BCRL). Humeral lymph nodes are a marker for deep lymphatic drainage. Epitrochlear lymph nodes are a site of superficial to deep collateralization based on cadaveric dissections. Functional connectivity between epitrochlear and humeral lymph nodes remains unexamined with in vivo imaging. We utilized lymphoscintigraphy to document epitrochlear and humeral lymph node drainage in healthy volunteers.

Methods: Healthy female volunteers received four intradermal hand/wrist injections of 99-Tcm sulfur colloid to each upper extremity and were imaged with SPECT/CT at 2 h. Two nuclear medicine physicians independently reviewed the SPECT/CT scans to document lymph nodes with tracer uptake. A Chi-square test was performed to assess the correlation between functional epitrochlear and humeral lymph node drainage.

Results: A total of 72 arms of 36 volunteers were included. Drainage to epitrochlear and humeral lymph nodes was observed in 57% (41/72) and 51% (37/72) of arms, respectively. Drainage to both epitrochlear and humeral lymph nodes was observed in 40% (29/72) of arms. Epitrochlear and humeral lymph node drainage were absent in 32% (27/72) of arms. The proportion of arms with humeral lymph node drainage was significantly greater in arms with (71%, 29/41) versus without (26%, 8/31) epitrochlear lymph node drainage [χ² = 14.262 (1), p < 0.001].

Conclusions: Epitrochlear and humeral lymph node drainage are significantly correlated, suggesting a superficial to deep pathway may function at baseline in 40% of arms. The absence of epitrochlear and humeral lymph node drainage may represent a biomarker for BCRL risk.