The Mascagni–Sappey (M–S) pathway is an alternative lymphatic drainage route in the lateral upper arm that typically runs alongside the cephalic vein and bypasses the standard axillary (underarm) lymph nodes; it typically terminates in the deltopectoral groove rather than the standard axillary lymph nodes. Anatomists Paolo Mascagni in 1787 and Marie Philippe Sappey in 1874 first documented the pathway. Sappey and Mascagni mapped these superficial lymphatic networks, and modern indocyanine green (ICG) lymphography has re-popularized visualizing this pathway to understand upper extremity lymphedema.
The Mascagni–Sappey (M–S) pathway is a secondary lymphatic drainage route of the lateral upper arm that courses along the cephalic vein, frequently terminating in the deltopectoral groove (near the collarbone) rather than the armpit. From there, it drains into higher-level clavicular and cervical lymph nodes. Studies using indocyanine green (ICG) lymphography show the pathway is not universal; it is absent in roughly 22% of individuals.
When primary axillary drainage is damaged, such as during axillary lymph node dissection or radiation therapy for breast cancer, the M–S pathway can act as a crucial collateral “back-up” system to drain fluid from the arm. Modern imaging like ICG lymphography helps surgeons visualize these alternative channels during procedures like lymphatic reconstruction to help prevent or lower the risk of chronic post-surgical lymphedema.
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Research
Granoff, M., Pardo, J., Shillue, K., et al. (2023). Variable anatomy of the lateral upper arm lymphatic channel: An anatomical risk factor for breast cancer-related lymphedema. Plastic and Reconstructive Surgery.
Johnson, A., Bravo, M., James, T., et al. (2020). The all but forgotten Mascagni-Sappey pathway: Learning from immediate lymphatic reconstruction. Journal of Reconstructive Microsurgery.
Johnson, A., Granoff, M., Suami, H., et al. (2020). Real-time visualization of the Mascagni-Sappey pathway utilizing ICG lymphography. Cancers.
Additional Information
Extramural funding: 5R01HL157991-05 Variable anatomy & function of the arm’s alternate lymphatic pathway | Beth Israel Deaconess Medical Center