Figure 2. Potential patterns of merging lymphatics. (A) Perilesional injection with sentinel node (SN) and more distant echelon node. (B) Surface injection augmenting perilesional injection, by far the most common pattern seen. (C) Pseudosentinel node (PSN) i.e. a dilation/ectasia representing focal pooling of activity along the lymphatic channel and a reverse echelon node (REN) representing a node seen "upstream" from the perilesional injection site. The original "true" SN also gets augmented, a pattern of partial discongruence. (D) Surface injection bypassing the true SN and visualizing a distant echelon node that might not contain tumour or another different node altogether, a pattern of complete discongruence. Adapted, modified from Krynycki BR et al [1] and used with permission from Lippincot, Williams & Wilkins, Philadelphia.