Intrathoracic eosinophilic sclerosing fibroplasia with intralesional bacteria in a cat.

Eosinophilic sclerosing fibroplasia is reportedly mainly confined to the gastrointestinal tract in cats. Less commonly, extragastrointestinal cases have been described. Lesions in the mediastinal or sternal lymph nodes have been reported, all in association with evident gastrointestinal involvement. The presence of pleural effusion was variable in these cases. To the authors' knowledge, this is the first report of eosinophilic sclerosing fibroplasia presenting due to lower respiratory signs in a cat. Intralesional bacteria were identified using Gram staining and FISH examination. The presence of intralesional bacteria in the normally sterile mediastinal tissue may support the involvement of penetrating injuries in the pathogenesis of the disease. Eosinophilic sclerosing fibroplasia should be suspected in any cat with abdominal and/or thoracic masses, particularly if associated with peripheral eosinophilia and polyclonal gammopathy.