Stomach, Forestomach - Hyperkeratosis

Hyperkeratosis is defined as thickening of the stratum corneum. It occurs in two forms: orthokeratotic or parakeratotic hyperkeratosis. In orthokeratotic hyperkeratosis (also referred to as orthokeratosis squamous epithelial cells are anuclear, whereas in parakeratotic hyperkeratosis (also referred to as parakeratosis) the squamous epithelial cells have retained pyknotic nuclei. Hyperkeratosis frequently accompanies hyperplasia (Figure 1 and Figure 2). Hyperkeratosis in the absence of hyperplasia should be diagnosed. It is a feature commonly present in anorectic rodents and has interpretative implications different from those of hyperkeratosis occurring as part of the process of enhanced epithelial proliferation. In the anorectic rodent, the excess keratin is presumably the result of reduced mechanical removal by the passage of food. In cases of hyperkeratosis in the forestomach associated with anorexia, hyperkeratosis is usually also present in the esophagus.