Cellular and molecular pathology of head and neck tumors

Head and neck pathology encompasses a multitude of organs of diverse histogenesis. Malignancies arising from head and neck sites accordingly are diverse in origins, morphogenesis, and biological behavior. Excluding connective tissue and vascular entities, the main entities that are presented in this chapter include squamous mucosal site, salivary, thyroid and sinonasal, and skull base tumors. The histopathological classification remains the main reference to the diagnosis and, to a large extent, malignancy grading. Advances in immunohistochemical techniques and the development of reagents to cellular intermediate filaments and lineage markers have led to better diagnosis and categorization of undifferentiated entities with overlapping morphologic features. More recently, major strides have been achieved in the molecular genetic characterization and understanding of head and neck tumorigenesis. Although clinically applicable and validated, molecular biomarkers have yet to be realized; it is important to address the recent discoveries and their potential integration with the phenotypic and pathologic features. This chapter concisely presents the relevant pathomorphologic and molecular features of the tumors of the major head and neck sites for clinical management.