In 1920, Nils Ragnar Eugène Antoni (1887–1968), a Swedish neurologist and researcher working at the Royal Neurologic Clinic of Stockholm under the supervision of the eminent neuropathologist and now controversial eugenics proponent Frithiof Lennmalm (1858–1924), described 2 distinct patterns of cellular architecture in the peripheral nerve sheath tumors, which would become known as schwannomas.

Antoni, who would later become professor of neurology at the Karolinska Institute in Stockholm, based his observations on analysis of 30 cases and described a “fibrillary, intensely polar, elongated appearing tissue type” which he called “tissue type A.”

These highly cellular regions were eventually referred to as Antoni A regions by later authors. Antoni also described seemingly distinct loose microcystic tissue adjacent to the Antoni A regions, and these came to be known as Antoni B regions. Recognition of these patterns has proved useful in the histologic identification of schwannomas.