NCIt definition : Hypertrophy of the outermost layer of the epidermis. It may be caused by physical
or chemical irritants, irradiation, infection, or neoplastic processes.;
Alternative definition : CDISC: Thickening of the outermost layer of stratified squamous epithelium.; NCI-GLOSS: A condition marked by thickening of the outer layer of the skin, which
is made of keratin (a tough, protective protein). It can result from normal use (corns,
calluses), chronic inflammation (eczema), or genetic disorders (X-linked ichthyosis,
ichthyosis vulgaris).;