This volume deals with tumours occurring in the following sites: Nasal cavity and paranasal sinuses Nasopharynx Larynx, hypopharynx and trachea External ear Middle and inner ear The classification of tumours arising from each of the anatomical sites listed above is given separately. However, since the same tu­ mour type may occur in more than one site, the definitions and il­ lustrations have been grouped together. The classification is based on the histological characteristics of the tumours and is therefore concerned with morphologically identifiable cell types and histo­ logical patterns as seen with conventional light microscopy. Al­ though many of the histological terms and definitions have histo­ genetic implications, this classification is not primarily based on histogenesis. The term "tumour" is used synonymously with neoplasm. The term "tumour-like" is applied to non-neoplastic lesions which clini­ cally or morphologically resemble neoplasms; they are included in this classification because of their importance in differential diag­ nosis. The terminology adopted for individual tumours is based on their general acceptance and world-wide usage. Synonyms are in­ cluded only if they have been widely used in the literature or if they are considered helpful in understanding the lesions. In such cases the preferred terms are given first followed by the synonyms within parentheses.