Crystals and crystalloids in cytopathology: Incidence and importance.

Many crystals and crystal-like structures may be encountered in cytopathology practice and can represent both beautiful novelties and diagnostic aids. The authors present an organ-specific review of the published literature on crystals combined with personal experiences. The purpose is not only to serve as a reference guide by highlighting the clinical and morphologic features of crystals, crystalloids, and crystal-like structures but also to review their significance and to offer reporting strategies in cases that bear management implications.