The term degeneration is used physiologically to refer to a process characterized by an impairment or perversion of the function of a tissue. It should be noted that with this definition cancer would be classified as a degeneration, and the expression "carcinomatous degeneration" of a tissue is not infrequently used.
Morphologically the degenerations form a heterogeneous group of changes in which abnormal materials collect in or between cells, with nonfatal or fatal consequences. The degenerations are believed to be due either to the metabolic disorder of cells, which arise from latent weaknesses in the constitution, or from external causative factors or a combination of both. The morphologic changes consist of "cloudy swelling," or albuminous degeneration, fatty degeneration, glycogen infiltration, amyloid degeneration, hyaline degeneration which involves collagenous connective tissue in arteriosclerosis, mucoid degeneration and the excessive deposit of urates, pigments, calcium and other substances and of the necrosis of cells.