Liesegang ringsLiesegang rings are laminated structures that are infrequently found in benign cystic lesions. The two most common sites are breast and kidney. Liesegang rings are most commonly seen in fine needle aspiration (FNA) cytology preparations but they can also be seen in histological tissue sections (see image on the right).
Structurally, Liesegang rings consist of a dense amorphous core surrounded by concentric layers of precipitate. The structure is formed by periodic precipitation of supersaturated colloid of the cyst content.
Liesegang rings have been historically confused with parasites (eggs of Dioctophyme renale, or giant kidney worm).
More broadly, the term Liesegang rings is used in chemistry to describe the concentric pattern of precipitation. The phenomenon of periodic precipitation was first described by Raphael Eduard Liesegang, a German chemist and photographer, in 1896.