Core C: Pathology SUMMARY/ ABSTRACT The individual research projects comprising this Ovarian Cancer SPORE application require the procurement, processing, and analysis of histopathological material from patients with ovarian cancer and benign ovarian diseases. The research projects have needs for frozen and formalin-fixed, paraffin-embedded samples of tumor and normal tissue. The research projects also need patient-derived xenograft models and organoids to test the effects of novel drugs and define the mechanisms of drug resistance. The proposed Pathology Core augments the already established MD Anderson Cancer Center Gynecological Tumor Bank and the P30- sponsored MD Anderson Cancer Center Centralized Tissue Repository with supporting database and intranet access. The Core provides for tissue acquisition by experienced gynecological pathologists to assure high- quality tissues for the investigators participating in this SPORE as well as investigators of other SPOREs. The goal of the Pathology Core is to provide frozen tissue, paraffin-embedded tissue, histopathological expertise, tissue arrays, patient-derived xenografts, and organoids related to the specific needs of the research projects comprising this SPORE proposal. To meet this goal, the following Specific Aims are proposed for this Core. Aim 1 is to maintain a frozen and paraffin-embedded tissue repository of ovarian cancers, normal ovaries, and benign ovarian processes (such as cysts and endometriosis). Aim 2 is to provide pathological review for all clinical specimens utilized in the SPORE projects and to provide histopathological and immunohistochemical technical services as necessary. Aim 3 is to create tissue microarrays, patient-derived xenografts (PDXs), and organoid models and maintain a relational SPORE Database. This SPORE Database will provide for a virtual tissue repository that can be shared electronically with all SPORE investigators.