Non-epitheliotropic cutaneous T-cell lymphoma in a 5-week-old golden retriever puppy

A 5-week-old male golden retriever puppy was presented with multiple, rapidly progressive skin masses. One of the masses had been present since birth; the duration of the other 2 masses was unknown. Fine-needle aspiration cytology of the lesions revealed a monomorphic population of round cells, raising suspicion for a round cell neoplasm. Two representative masses were submitted for histologic examination and immunohistochemical analysis. Histologically, the neoplasm was composed of dense, non-epitheliotropic infiltrates of atypical lymphoid cells within the dermis and subcutis. Immunophenotyping confirmed a T-cell origin, establishing a diagnosis of non-epitheliotropic cutaneous T-cell lymphoma. In the postoperative period, the puppy's health declined and humane euthanasia was elected. A postmortem examination did not occur, precluding assessment for systemic involvement. To the authors' knowledge this is the first case of non-epitheliotropic cutaneous T-cell lymphoma in a dog of this age documented in the veterinary literature. This report underscores the importance of including cutaneous lymphoma in the differential diagnosis of rapidly progressive skin masses in a dog, irrespective of age, and highlights the utility of histopathology and immunohistochemistry for achieving a diagnosis. Key clinical message: Lymphoma can occur in dogs of any age and should not be excluded as a differential diagnosis, even in very young puppies.