thymus atrophy thymus cortex atrophy atrophic thymus cortex thymic cortex atrophy acquired diminution of the outer part of a thymus lobule that surrounds the medulla and is composed of closely packed lymphocytes, associated with wasting as from death and reabsorption of cells, diminished cellular proliferation, decreased cellular volume, pressure, ischemia, malnutrition, reduced function or malfunction, or hormonal changes MP:0013585 atrophic thymic cortex small thymus cortex cortex of thymus atrophy