feline lymphosarcoma

[AlW1]

I am a practicing veterinarian and don't have my books near the computer
to reference what I am going to say, but FELV negative lymphosarcomas are
relatively common. It used to be (and I think still is) thought that most
of these tumors are still due to the FELV virus, it just isn't found with
the usual tests. The virus has done its damage and been eliminated from
the circulation.