As we learn more and more about the molecular pathogenesis of tumors, assays in molecular diagnostics are permeating into the clinical every-day practice of anatomic pathology. This means that tumors we used to diagnose with a 1-line diagnosis and an assessment of margins are now quickly becoming more complicated in both the workup and the reporting. The pathologist must now go beyond the hematoxylin-eosin slide and the usual tumor parameters and now take into account diagnostic, prognostic, and therapeutic markers that might be available. No matter what the organ system, the anatomic pathologist is well suited to take on the role of pulling together diverse information from various biological assays, and interpreting results in the context of the morphologic diagnoses. While there are challenges, particularly because of the rapid and constant evolution of the standard of care, this role will also be one of the most important and rewarding ones that we can have, as we continue to lead and participate in the diagnosis management of our patients' diseases.

In the head and neck, there has been an explosion of important information at the molecular level, both about tumors and inflammatory conditions. This has spanned across almost every anatomic subsite in the head and neck, as well as across tumor types and conditions. Exciting new developments in molecular pathology have challenged some basic tumor classifications, have elucidated new entities, and have changed the way we manage and treat some common conditions. Perhaps the most exciting developments have been in the area of new treatments that are based either on better molecular classification and understanding of disease, or based on novel therapeutic targets. There are new biomarkers being described and clinically validated regularly. From inflammatory conditions, to benign neoplastic entities, to common and rare tumors, our diagnostic algorithms are changing rapidly along with our growing understanding of molecular pathogenesis.

The following collection of articles covers new information about the molecular etiology of some common and uncommon head and neck lesions that we face in clinical practice. While there is a focus on the known and evolving molecular pathogenesis, the authors have also highlighted the clinical practical applications that the pathologist must consider when reporting these entities. Though not comprehensive or exhaustive, these selections give us insight into specific entities and also reveal the rapid evolution that we can expect in the coming decade, as we strive to incorporate more and more molecular diagnostics into the routine anatomic pathology work we do in practice.