Spontaneous resolving of eosinophilic granulomatous pneumonia was observed in a F344 rat. Although the pulmonary lesions were observed in a rat, lesions with different histopathological features were found in this rat. Lesions showing initial stage of...
Spontaneous resolving of eosinophilic granulomatous pneumonia was observed in a F344 rat. Although the pulmonary lesions were observed in a rat, lesions with different histopathological features were found in this rat. Lesions showing initial stage of eosinophilic pneumonia demonstrated edema of perivascular and peribronchial connective tissue and infiltration of eosinophils in these areas. With progress of the lesions, microgranulomas were formed by the infiltration of eosinophils, mononuclear cells, and pulmo¬nary foam cells. With unknown reasons, the granulomatous lesions were regressed with apoptosis of eosinophils. The present paper describes the pathological aspects of the lesions in F344 rat and discusses the pathogenesis of tissue injury related to eosinophilic pneumonia.