Unicystic Ameloblastoma : Microscopic
Three subtypes of unicystic ameloblastoma have been described depending upon the location and arrangement of the epithelium. Luminal type (shown here): The neoplastic epithelium is confined to the luminal surface of the cyst i.e. the lesion consists of a simple unilocular cyst with a fibrous wall and lined partially or completely by multiple layers of ameloblastic epithelium. The basal portion of the lining epithelium is tall columnar or cuboidal with peripheral palisading and reverse polarity (nuclei oriented away from the basement membrane). The peripheral portion (towards the luminal aspect) is composed of loosely cohesive cells resembling stellate reticulum. Intraluminal type: In the intraluminal unicystic ameloblastoma, one or more nodules of ameloblastic epithelium project into the cyst lumen. The nodules may be small or large enough to fill the cyst lumen. Mural type: The mural unicystic ameloblastoma consists of typical islands of ameloblastic cells in follicular or plexiform pattern infiltrating the cyst wall.