Feline Lymphoma Feline Lymphoma And Leukemia Connection In Young Cats...?

Feline lymphoma and leukemia connection in young cats...? - feline lymphoma

I had a cat who is one years after his death of renal lymphoma was (and died a few months after his diagnosis), despite treatment. He tested negative for feline leukemia virus (FeLV). I also have his brother, who was born in the same extent. His brother looks healthy, and were negative for FeLV.

However, it is possible that the real cat with lymphoma were FeLV-NO? If it is not unlikely that patients of lymphoma within a year to die in another way?

I fear that his brother will develop lymphoma or are currently infected with leukemia, and despite the negative result. Is it possible that the kitten's lymphoma in reality, than others and that the mine could be affected?