Functional variation in lymph node arrangements within the axilla.

The aim of the project was to identify how lymphatic pathways are functionally arranged within the axilla (i.e., single linear chains, branching chains, and networks). We used ex vivo dual isotope radioassay of individual nodes resected at axillary lymphatic clearance surgery in breast cancer patients given simultaneous intradermal breast and intradermal hand injections (n = 15) or simultaneous intradermal breast and parenchymal breast injections (n = 15) of differentially labelled human immunoglobulin (Tc-99m-HIG and In-111-HIG). Nodes were ranked according to isotope content and activity-rank profiles constructed for each of the two injection sites. The majority of profiles following intradermal breast injection (17/30) were mono-exponential, consistent with a simple linear chain of nodes, with each node extracting a constant fraction of incoming HIG. In 15/17 of these, the accompanying profile from the alternative injection site was also mono-exponential and, in 11/15, essentially parallel. The profile appeared biphasic in 12/30 intradermal breast injections and of these 9/12 were accompanied by a biphasic profile (7/9 parallel) from the alternative injection site. In one patient, both profiles were polyphasic and parallel. Considering the respective shapes of paired profiles and whether the two injection sites shared the same first echelon nodes, functional lymph node arrangements are proposed. The commonest is a single linear chain, then a chain branching into two linear chains, and, least common, a network.