Adrenal Gland - Inflammation

Inflammation of the adrenal gland is uncommon in F344/N rats and B6C3F1/N mice. It is usually secondary to systemic disease or as an extension of inflammation in adjacent tissues, such as the kidney or retroperitoneal fat. Adrenal gland inflammation must be distinguished from extramedullary hematopoiesis (foci of immature hematopoietic cells) and from systemic lymphoid or hematopoietic neoplastic infiltrates (poorly differentiated, often anaplastic cells usually in extensive accumulations that distort or obliterate normal glandular architecture).

In NTP studies, there are five standard categories of inflammation: acute, suppurative, chronic, chronic-active, and granulomatous. Acute inflammation is characterized by infiltration of neutrophils (Figure 1 and Figure 2), which may be accompanied by eosinophils and macrophages, and occasional mast cells, lymphocytes, and plasma cells. Suppurative inflammation is characterized by discrete pockets of degenerate neutrophils and cellular debris. There may be evidence of chronicity, such as fibrosis and lymphoplasmacytic infiltrates, surrounding these pockets. Chronic inflammation is characterized by the presence of mononuclear cells (lymphocytes, macrophages, and plasma cells) and may be accompanied by fibrosis. Chronic-active inflammation is characterized by coexistence of elements of chronic inflammation (lymphocytes, macrophages, fibrosis) and superimposed acute inflammation (neutrophilic and/or eosinophilic infiltrates). Granulomatous inflammation is characterized by accumulations of macrophages, multinucleated giant cells, and variable numbers of lymphocytes and plasma cells, or neutrophils. Inflammation is differentiated from cellular infiltrates by the presence of other changes, such as edema, hemorrhage, degeneration, necrosis, or other evidence of tissue damage.