pathology, study of the cause of disease and the modifications in cellular function and changes in cellular structure produced in any cell, organ, or part of the body by disease. The changes in tissue include degeneration, atrophy, hypertrophy, hyperplasia, and inflammation. The microscope is an important factor in detecting tissue changes, especially in the examination of small sections of tissue removed for diagnosis (biopsy); for this reason real progress in pathology was not made until the 19th cent. Other diagnostic techniques for testing body fluids and tissues for abnormal composition or metabolisms are electronmicroscopy, immunocytochemistry, and molecular pathologies.
See E. R. Long, A History of Pathology (1962, repr. 1965); W. A. Anderson and T. M. Scotti, Synopsis of Pathology (8th ed. 1972); L. V. Crowley, Introductory Concepts in Pathology (1972); L. Crowley, Introduction to Human Disease (1989).