Core C: Tissue and Histopathology Core will provide fundamental support services to the research investigators in the proposed UCSF Oral Cancer Research Center. The Core is an organized network of clinicians, pathologists, and technical staff whose aims are: (1) to make available human oral cancerous and precancerous tissues for applied research investigations, (2) to develop a patient database for correlation of patient outcome with molecular tumor markers, and (3) to provide basic technical and interpretive histologic and immunohistologic services to Center investigators. The Core will be directed by an experienced academic faculty: an oral pathologist assisted by a general pathologist and an oral clinical oncologist. Contributor-collaborators will be head and neck surgeons and oral medicine and oncology clinicians. A data manager and a laboratory technician will provide the necessary internal support services of patient follow-up and tissue management. Biopsies and surgical specimens with a diagnosis of oral epithelial dysplasia, carcinoma in situ, invasive carcinoma, and verrucal carcinoma will be included in the Core. Tissue will come from new patients treated at one of five UCSF clinical sites, and from the pathology archives of five UCSF hospitals and two large San Francisco oral pathology biopsy services (UCSF and University of the Pacific). A secondary source of tissue will be five additional California oral pathology services and two West Coast oral medicine clinics. More than 3,000 archived oral cancers and precancers are immediately available for study, and it is estimated that 125 new tumors will be accessioned annually from the San Francisco Bay Area for use in prospective studies. Banked tissues will support the research projects that are the substance of the proposed center, and they will also be fundamental to the collection of demographic and follow-up data for oral cancer and precancer patients.