Comparative Pathology Shared Resource Summary The mission of the Masonic Cancer Center (MCC) Comparative Pathology Shared Resource (CPSR) is to provide comprehensive and ever-evolving support and training in all aspects of comparative pathology to MCC members in a cost-effective manner. The CPSR is a critical resource for projects using animals and animal tissues and is essential for the generation of high-quality publications, presentations, and grants. The CPSR Director is Davis Seelig, DVM, PhD, DACVP, and he is supported by Technical Coordinator Katalin Kovacs, PhD; histotechnologist Paula Overn, HT, QIHC; and postdoctoral research pathologist, Emma Torii, BVSc, MANZCVS (Pathobiology), DACVP. Dr. Seelig replaced the previous director of the CPSR, Dr. M. Gerard O’Sullivan, in April 2021. Like his predecessor, he brings extensive (>15 years) experience in comparative and experimental veterinary pathology. Uniquely, he also brings expertise in veterinary anatomic and clinical pathology as well as in comparative neuropathology. The CPSR offers comprehensive pathology support that encompasses study planning through data presentation for publication and grant submission. We offer training and oversight during the tissue collection phase and prepare appropriately processed fixed or frozen tissues for histology and immunohistochemistry (IHC). Particular strengths of the laboratory are in the performance of nonroutine, challenging, or tedious histological preparations; performing IHC preparations on multiple markers; developing new IHC protocols for markers of interest; providing researchers with comprehensive and holistic study reports; and performing IHC on bone. Two board-certified veterinary pathologists (Drs. Seelig and Torii) provide expert gross and histopathologic analysis, generate high-resolution digital images of specimens, and provide intellectual input on study design and manuscript preparation for research projects and grant applications. Chargeback systems are in place for all services offered by the CPSR. In fiscal year 2022, 44 individuals used CPSR services, of whom 27 were MCC members.