A scapular node was a physiological component.

In 2369, Doctor Julian Bashir examined the scapular nodes of a seemingly dead woman for a parasitic infection and discovered that the woman was actually alive, despite tricorder readings that said otherwise. (DS9: "The Passenger")

It was not mentioned in what part of the body scapular nodes are located, or in what species or lifeforms. The term scapular typically refers to the scapula, or shoulder bone, and prescapular lymph nodes are located just in front of the shoulders. Since it was mentioned that the nodes were located in a woman, it can be inferred that scapular nodes are found in shoulder region of humanoids.