Progression of primary mediastinal T-cell lymphoma to a multicentric form in a young dog.

drug sensitivity testing, lomustine was initiated as rescue chemotherapy, achieving a second complete remission. Nevertheless, relapse occurred 38 d after the initial lomustine administration, and the dog ultimately died. Key clinical message: This case highlights the fact that progression from primary mediastinal to multicentric lymphoma may be associated with a poor prognosis in dogs. Radiation therapy demonstrated potential efficacy and warrants further investigation as a treatment option for canine mediastinal lymphoma.