Multisystemic, eosinophilic, epitheliotropic disease with intestinal lymphosarcoma in a horse.

The research presents a case of a Paso Fino mare suffering from a multisystemic, eosinophilic, epitheliotropic disease combined with intestinal lymphosarcoma. These conditions were identified following the horse exhibiting symptoms of anorexia and weight loss.

Analysis of the Horse’s Condition

• The horse was diagnosed with both multisystemic, eosinophilic, epitheliotropic disease and intestinal lymphosarcoma. These conditions were identified when the horse displayed symptoms of anorexia (loss of appetite) and a consequential loss of weight.
• The researchers found several organs notably, the stomach, ileum, cecum, colon, pancreas, and lungs, were affected. These organs had been infiltrated by large quantities of eosinophils, thereby forming distinguishable eosinophilic granulomas, as well as lymphocytes and plasma cells. A high concentration of eosinophils can lead to granulomas; these are masses of granulation tissue, typically produced in response to infection, inflammation, or the presence of a foreign substance.

Neoplastic Lymphocytes and T-cell Lymphosarcoma

• Two masses composed entirely of neoplastic lymphocytes were found in the horse’s jejunum (a part of the small intestine). These particular infiltrates did not contain any of the plasma cells, eosinophils, or eosinophilic granulomas that were found elsewhere in the horse’s body.
• After conducting immunohistochemical analysis, the researchers found that these neoplastic lymphocytes expressed CD3, a crucial part of the T-cell receptor complex, but neither CD20 nor kappa and lambda light chains. This finding strongly supported a diagnosis of T-cell lymphosarcoma, a type of lymphoid cancer that affects T lymphocytes.

Link between Hypereosinophilic Syndrome and Lymphosarcoma

• The case of this horse, combined with various human cases, led the researchers to propose that the multisystemic eosinophilic and lymphoplasmacytic infiltrates were a result of the clonal proliferation of T-lymphocytes.
• These T-lymphocytes produce interleukin-5, which is capable of triggering the differentiation and activation of eosinophils. This process may lead to conditions such as hypereosinophilic syndrome (a blood disorder that leads to overproduction of eosinophils) and lymphosarcoma (a type of cancer in lymphoid tissues).