Associated with atelectasis or obstructive pneumonitis that extends to the hilar region but does not involve the entire lung.

When the nodules are centered around the hilar regions, the chest x-ray may develop what is called the "butterfly," or "batwing" appearance.

The SC are vestiges of the cranial portion of the mesonephric tubules and ducts, and in the adult ovary appear as a cluster of blind tubules in the hilar region.

It has also been shown that the axons of granule cells synapse with a wide variety of inhibitory GABA interneurons in the hilar region of the dentate gyrus before continuing on to innervate pyramidal cells in the CA3 region.