The World Health Organization's revised classification of tumours of the larynx, hypopharynx, and trachea.

A second edition of the Histological Typing of Upper Respiratory Tract Tumours in the WHO series International Histological Classification of Tumours was published in 1991. The new edition has been entitled Histological Typing of Tumours of the Upper Respiratory Tract and Ear. The task of revising the first edition, which was published in 1978, was undertaken at the WHO Center for Upper Respiratory Tract Tumours by K. Shanmugaratnam in collaboration with L. H. Sobin and pathologists in 8 countries. Several tumour types have been added to the classification, and some have been redefined in light of current knowledge. This presentation outlines the changes in the revised WHO classification as regards tumours of the larynx, hypopharynx, and trachea and discusses the grounds for said revisions.