Pathology is the scientific study of disease processes that affect normal anatomy and physiology. Anatomical and physiological changes are pathological changes when they result from an underlying disease process or abnormality.

Pathologists play an increasingly important role in diagnosis, research, and in the development of clinical treatments for disease. A specialized branch of pathology, forensic pathology, offers a vast array of molecular diagnostic techniques (including DNA fingerprint analysis) toward identification of remains, gathering of evidence, and identification of suspects.

Modern pathology labs rely heavily on molecular biology techniques and advances in biotechnology. During the last two decades, there have been tremendous advances in linking changes in cellular or tissue morphology (i.e., gross appearance) with genetic and/or intracellular changes. In many cases, specific molecular tests can definitively identify disease process, and of critical importance to the treatment of disease, and make a correct diagnosis at an earlier stage in the disease process.

Pathologists attempt to relate observable changes to disease process. Whether the changes are evident morphologically--or are distinguishable only via sophisticated molecular tests--the goal is to determine the existence and/or etiology of disease (the cause of disease). Once the etiologic agents are identified, the general goal of research is to document and gather evidence of the pathogenesis of disease (i.e., the mechanisms by which etiologic agents cause disease).

On a daily basis, pathologists perform a broad spectrum of tests on clinical samples to determine anatomical and physiological changes associated with a number of disease processes, including the detection of cancerous cells and tumors.

Major branches of pathology include the study of anatomic, cellular, and molecular pathology. Specific clinical studies often focus on transplantation pathology, neuropathology, immunopathology, virology, parasitology, and a number of clinical subspecialties (e.g. pediatric pathology).